Vanessa Kosoy's Shortform

post by Vanessa Kosoy (vanessa-kosoy) · 2019-10-18T12:26:32.801Z · LW · GW · 80 comments


Comments sorted by top scores.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-26T15:28:53.199Z · LW(p) · GW(p)

An AI progress scenario which seems possible and which I haven't seen discussed: an imitation plateau.

The key observation is, imitation learning algorithms[1] might produce close-to-human-level intelligence even if they are missing important ingredients of general intelligence that humans have. That's because imitation might be a qualitatively easier task than general RL. For example, given enough computing power, a human mind becomes realizable from the perspective of the learning algorithm, while the world-at-large is still far from realizable. So, an algorithm that only performs well in the realizable setting can learn to imitate a human mind, and thereby indirectly produce reasoning that works in non-realizable settings as well. Of course, literally emulating a human brain is still computationally formidable, but there might be middle scenarios where the learning algorithm is able to produce a good-enough-in-practice imitation of systems that are not too complex.

This opens the possibility that close-to-human-level AI will arrive while we're still missing key algorithmic insights to produce general intelligence directly. Such AI would not be easily scalable to superhuman. Nevertheless, some superhuman performance might be produced by sped-up simulation, reducing noise in human behavior and controlling the initial conditions (e.g. simulating a human on a good day). As a result, we will have some period of time during which AGI is already here, automation is in full swing, but there's little or no further escalation. At the end of this period, the missing ingredients will be assembled (maybe with the help of AI researchers) and superhuman AI (possibly a fast takeoff) begins.

It's interesting to try and work out the consequences of such a scenario, and the implications on AI strategy.

  1. Such as GPT-n ↩︎

comment by Vladimir_Nesov · 2020-09-27T09:13:29.894Z · LW(p) · GW(p)

This seems similar to gaining uploads prior to AGI, and opens up all those superorg upload-city amplification/distillation constructions which should get past human level shortly after. In other words, the limitations of the dataset can be solved by amplification as soon as the AIs are good enough to be used as building blocks for meaningful amplification, and something human-level-ish seems good enough for that. Maybe even GPT-n is good enough for that.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-27T10:30:29.646Z · LW(p) · GW(p)

That is similar to gaining uploads (borrowing terminology from Egan, we can call them "sideloads"), but it's not obvious amplification/distillation will work. In the model based on realizability, the distillation step can fail because the system you're distilling is too computationally complex (hence, too unrealizable). You can deal with it by upscaling the compute of the learning algorithm, but that's not better than plain speedup.

comment by Vladimir_Nesov · 2020-09-27T11:23:13.138Z · LW(p) · GW(p)

To me this seems to be essentially another limitation of the human Internet archive dataset: reasoning is presented in an opaque way (most slow/deliberative thoughts are not in the dataset), so it's necessary to do a lot of guesswork to figure out how it works. A better dataset both explains and summarizes the reasoning (not to mention gets rid of the incoherent nonsense, but even GPT-3 can do that to an extent by roleplaying Feynman).

Any algorithm can be represented by a habit of thought (Turing machine style if you must), and if those are in the dataset, they can be learned. The habits of thought that are simple enough to summarize get summarized and end up requiring fewer steps. My guess is that the human faculties needed for AGI can be both represented by sequences of thoughts (probably just text, stream of consciousness style) and easily learned with current ML. So right now the main obstruction is that it's not feasible to build a dataset with those faculties represented explicitly that's good enough and large enough for current sample-inefficient ML to grok. More compute in the learning algorithm is only relevant for this to the extent that we get a better dataset generator that can work on the tasks before it more reliably.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-27T11:46:46.882Z · LW(p) · GW(p)

I don't see any strong argument why this path will produce superintelligence. You can have a stream of thought that cannot be accelerated without investing a proportional amount of compute, while a completely different algorithm would produce a far superior "stream of thought". In particular, such an approach cannot differentiate between features of the stream of thought that are important (meaning that they advance towards the goal) and features of the stream of though that are unimportant (e.g. different ways to phrase the same idea). This forces you to solve a task that is potentially much more difficult than just achieving the goal.

comment by Vladimir_Nesov · 2020-09-27T12:30:48.120Z · LW(p) · GW(p)

I was arguing that near human level babblers (including the imitation plateau you were talking about) should quickly lead to human level AGIs by amplification via stream of consciousness datasets, which doesn't pose new ML difficulties other than design of the dataset. Superintelligence follows from that by any of the same arguments as for uploads leading to AGI (much faster technological progress; if amplification/distillation of uploads is useful straight away, we get there faster, but it's not necessary). And amplified babblers should be stronger than vanilla uploads (at least implausibly well-educated, well-coordinated, high IQ humans).

For your scenario to be stable, it needs to be impossible (in the near term) to run the AGIs (amplified babblers) faster than humans, and for the AGIs to remain less effective than very high IQ humans. Otherwise you get acceleration of technological progress, including ML. So my point is that feasibility of imitation plateau depends on absence of compute overhang, not on ML failing to capture some of the ingredients of human general intelligence.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-27T13:09:15.277Z · LW(p) · GW(p)

The imitation plateau can definitely be rather short. I also agree that computational overhang is the major factor here. However, a failure to capture some of the ingredients can be a cause of low computational overhead, whereas a success to capture all of the ingredients is a cause of high computational overhang, because the compute necessary to reach superintelligence might be very different in those two cases. Using sideloads to accelerate progress might still require years, whereas an "intrinsic" AGI might lead to the classical "foom" scenario.

EDIT: Although, since training is typically much more computationally expensive than deployment, it is likely that the first human-level imitators will already be significantly sped-up compared to humans, implying that accelerating progress will be relatively easy. It might still take some time from the first prototype until such an accelerate-the-progress project, but probably not much longer than deploying lots of automation.

comment by Vladimir_Nesov · 2020-09-27T14:13:34.873Z · LW(p) · GW(p)

I agree. But GPT-3 seems to me like a good estimate for how much compute it takes to run stream of consciousness imitation learning sideloads (assuming that learning is done in batches on datasets carefully prepared by non-learning sideloads, so the cost of learning is less important). And with that estimate we already have enough compute overhang to accelerate technological progress as soon as the first amplified babbler AGIs are developed, which, as I argued above, should happen shortly after babblers actually useful for automation of human jobs are developed (because generation of stream of consciousness datasets is a special case of such a job).

So the key things to make imitation plateau last for years are either sideloads requiring more compute than it looks like (to me) they require, or amplification of competent babblers into similarly competent AGIs being a hard problem that takes a long time to solve.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-27T16:16:12.611Z · LW(p) · GW(p)

Another thing that might happen is a data bottleneck.

Maybe there will be a good enough dataset to produce a sideload that simulates an "average" person, and that will be enough to automate many jobs, but for a simulation of a competent AI researcher you would need a more specialized dataset that will take more time to produce (since there are a lot less competent AI researchers than people in general).

Moreover, it might be that the sample complexity grows with the duration of coherent thought that you require. That's because, unless you're training directly on brain inputs/outputs, non-realizable (computationally complex) environment influences contaminate the data, and in order to converge you need to have enough data to average them out, which scales with the length of your "episodes". Indeed, all convergence results for Bayesian algorithms we have in the non-realizable setting require ergodicity, and therefore the time of convergence (= sample complexity) scales with mixing time, which in our case is determined by episode length.

In such a case, we might discover that many tasks can be automated by sideloads with short coherence time, but AI research might require substantially longer coherence times. And, simulating progress requires by design going off-distribution along certain dimensions which might make things worse.

comment by avturchin · 2020-09-26T17:14:48.960Z · LW(p) · GW(p)

Another way to describe the same (or similar) plateau: we could think about GPT-n as GLUT with approximation between prerecorded answers: it can produce intelligent products similar to the ones which were created by humans in the past and are presented in its training dataset – but not above the human intelligence level, as there is no superintelligent examples in the dataset. 

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-03-23T16:17:45.672Z · LW(p) · GW(p)

I have [AF(p) · GW(p)] repeatedly [AF(p) · GW(p)] argued [AF(p) · GW(p)] for a departure from pure Bayesianism that I call "quasi-Bayesianism". But, coming from a LessWrong-ish background, it might be hard to wrap your head around the fact Bayesianism is somehow deficient. So, here's another way to understand it, using Bayesianism's own favorite trick: Dutch booking!

Consider a Bayesian agent Alice. Since Alice is Bayesian, ey never randomize: ey just follow a Bayes-optimal policy for eir prior, and such a policy can always be chosen to be deterministic. Moreover, Alice always accepts a bet if ey can choose which side of the bet to take: indeed, at least one side of any bet has non-negative expected utility. Now, Alice meets Omega. Omega is very smart so ey know more than Alice and moreover ey can predict Alice. Omega offers Alice a series of bets. The bets are specifically chosen by Omega s.t. Alice would pick the wrong side of each one. Alice takes the bets and loses, indefinitely. Alice cannot escape eir predicament: ey might know, in some sense, that Omega is cheating em, but there is no way within the Bayesian paradigm to justify turning down the bets.

A possible counterargument is, we don't need to depart far from Bayesianism to win here. We only need to somehow justify randomization, perhaps by something like infinitesimal random perturbations of the belief state (like with reflective oracles). But, in a way, this is exactly what quasi-Bayesianism does: a quasi-Bayes-optimal policy is in particular Bayes-optimal when the prior is taken to be in Nash equilibrium of the associated zero-sum game. However, Bayes-optimality underspecifies the policy: not every optimal reply to a Nash equilibrium is a Nash equilibrium.

This argument is not entirely novel: it is just a special case of an environment that the agent cannot simulate, which is the original motivation for quasi-Bayesianism. In some sense, any Bayesian agent is dogmatic: it dogmatically beliefs that the environment is computationally simple, since it cannot consider a hypothesis which is not. Here, Omega exploits this false dogmatic belief.

comment by Dagon · 2020-03-23T17:22:39.317Z · LW(p) · GW(p)

Bayeseans are allowed to understand that there are agents with better estimates than they have. And that being offered a bet _IS_ evidence that the other agent THINKS they have an advantage.

Randomization (aka "mixed strategy") is well-understood as the rational move in games where opponents are predicting your choices. I have read nothing that would even hint that it's unavailable to Bayesean agents. The relevant probability (updated per Bayes's Rule) would be "is my counterpart trying to minimize my payout based on my choices".

edit: I realize you may be using a different definition of "bayeseanism" than I am. I'm thinking humans striving for rational choices, which perforce includes the knowledge of incomplete computation and imperfect knowledge. Naive agents can be imagined that don't have this complexity. Those guys are stuck, and Omega's gonna pwn them.

comment by mr-hire · 2020-03-23T17:41:53.796Z · LW(p) · GW(p)

I'm thinking humans striving for rational choices,

It feels like there's better words for this like rationality, whereas bayesianism is a more specific philosophy about how best to represent and update beliefs.

comment by Pattern · 2020-03-25T07:11:20.152Z · LW(p) · GW(p)

And here I thought the reason was going to be that Bayesianism doesn't appear to include the cost of computation. (Thus, the usual dutch book arguments should be adjusted so that "optimal betting" does not leave one worse off for having payed, say, an oracle, too much for computation.)

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-26T14:42:47.388Z · LW(p) · GW(p)

Game theory is widely considered the correct description of rational behavior in multi-agent scenarios. However, real world agents have to learn, whereas game theory assumes perfect knowledge, which can be only achieved in the limit at best. Bridging this gap requires using multi-agent learning theory to justify game theory, a problem that is mostly open (but some results exist). In particular, we would like to prove that learning agents converge to game theoretic solutions such as Nash equilibria (putting superrationality aside: I think that superrationality should manifest via modifying the game rather than abandoning the notion of Nash equilibrium).

The simplest setup in (non-cooperative) game theory is normal form games. Learning happens by accumulating evidence over time, so a normal form game is not, in itself, a meaningful setting for learning. One way to solve this is replacing the normal form game by a repeated version. This, however, requires deciding on a time discount. For sufficiently steep time discounts, the repeated game is essentially equivalent to the normal form game (from the perspective of game theory). However, the full-fledged theory of intelligent agents requires considering shallow time discounts, otherwise there is no notion of long-term planning. For shallow time discounts, the game theory of a repeated game is very different from the game theory of the original normal form game. In fact, the folk theorem asserts that any payoff vector above the maximin of each player is a possible Nash payoff. So, proving convergence to a Nash equilibrium amounts (more or less) to proving converges to at least the maximin payoff. This is possible using incomplete models [AF · GW], but doesn't seem very interesting: to receive the maximin payoff, the agents only have to learn the rules of the game, they need not learn the reward functions of the other players or anything else about them.

We arrive at the question, what setting is realistic (in the sense of involving learning with shallow time discount) and is expected to produce Nash equilibria for a normal form game? I suggest the following. Instead of a fixed set of agents repeatedly playing against each other, we consider a population of agents that are teamed-off randomly on each round of the game. The population is assumed to be large enough for agents not to encounter each other more than once. This can be formalized as follows. Let be the pure strategy set of the -th agent and the set of pure outcomes. The set of -round outcome histories is . The population of agents on the -round can then be described as a probability measure . Suppose the policy of the -th player (that is, of all the agents that take the role of the -th player) is . Then we can define a time evolution rule that produces from . This rule works as follows: in order to sample we sample once per player (this is the history the given player has seen), sample the policy of each player on its own history, and produce a new history by appending the resulting outcome to one of the old histories (it doesn't matter which). A set of policies is considered to be in equilibrium, when for any , and any alternative policy , letting play against the same population (i.e. all other copies of the -th player still play ) doesn't improve expected utility. In other words, on each round the "mutant" agent retains its own history but the other player histories are still sampled from the same . It is easy to see that any equilibrium payoff in this setting is a Nash payoff in the original normal form game. We can then legitimately ask whether taking the to be learning algorithms would result in convergence to a Nash payoff in the (shallow time discount) limit.

For example, consider the Prisoner's dilemma. In the repeated Prisoner's dilemma with shallow time discount, is an equilibrium because of the tit-for-tat policy. On the other hand, in the "population" (massively multi-player?) repeated Prisoner's dilemma, is the only equilibrium. Tit-for-tat doesn't work because a single "defect bot" can exploit a population of tit-for-tats: on each round it plays with a new opponent that doesn't know the defect bot defected on the previous round.

Note that we get a very different setting if we allow the players to see each other's histories, more similar (equivalent?) to the regular repeated game. For example, in the Prisoner's Dilemma we have a version of tit-for-tat that responds to what its current opponent played in its previous round (against a different opponent). This may be regarded as a confirmation of the idea that agents that know each other's source code are effectively playing a repeated game: in this setting, knowing the source code amounts to knowing the history.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-01T16:03:19.620Z · LW(p) · GW(p)

We can modify the population game setting to study superrationality. In order to do this, we can allow the agents to see a fixed size finite portion of the their opponents' histories. This should lead to superrationality for the same reasons I discussed [AF(p) · GW(p)] before. More generally, we can probably allow each agent to submit a finite state automaton of limited size, s.t. the opponent history is processed by the automaton and the result becomes known to the agent.

What is unclear about this is how to define an analogous setting based on source code introspection. While arguably seeing the entire history is equivalent to seeing the entire source code, seeing part of the history, or processing the history through a finite state automaton, might be equivalent to some limited access to source code, but I don't know to define this limitation.

EDIT: Actually, the obvious analogue is processing the source code through a finite state automaton.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-08T17:39:38.596Z · LW(p) · GW(p)

Instead of postulating access to a portion of the history or some kind of limited access to the opponent's source code, we can consider agents with full access to history / source code but finite memory. The problem is, an agent with fixed memory size usually cannot have regret going to zero, since it cannot store probabilities with arbitrary precision. However, it seems plausible that we can usually get learning with memory of size . This is because something like "counting pieces of evidence" should be sufficient. For example, if consider finite MDPs, then it is enough to remember how many transitions of each type occurred to encode the belief state. There question is, does assuming memory (or whatever is needed for learning) is enough to reach superrationality.

comment by Gurkenglas · 2019-12-07T13:03:57.992Z · LW(p) · GW(p)

What do you mean by equivalent? The entire history doesn't say what the opponent will do later or would do against other agents, and the source code may not allow you to prove what the agent does if it involves statements that are true but not provable.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-07T22:39:29.289Z · LW(p) · GW(p)

For a fixed policy, the history is the only thing you need to know in order to simulate the agent on a given round. In this sense, seeing the history is equivalent to seeing the source code.

The claim is: In settings where the agent has unlimited memory and sees the entire history or source code, you can't get good guarantees (as in the folk theorem for repeated games). On the other hand, in settings where the agent sees part of the history, or is constrained to have finite memory (possibly of size ?), you can (maybe?) prove convergence to Pareto efficient outcomes or some other strong desideratum that deserves to be called "superrationality".

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-10T12:52:46.072Z · LW(p) · GW(p)

In the previous "population game" setting, we assumed all players are "born" at the same time and learn synchronously, so that they always play against players of the same "age" (history length). Instead, we can consider a "mortal population game" setting where each player has a probability to die on every round, and new players are born to replenish the dead. So, if the size of the population is (we always consider the "thermodynamic" limit), players die and the same number of players are born on every round. Each player's utility function is a simple sum of rewards over time, so, taking mortality into account, effectively ey have geometric time discount. (We could use age-dependent mortality rates to get different discount shapes, or allow each type of player to have different mortality=discount rate.) Crucially, we group the players into games randomly, independent of age.

As before, each player type chooses a policy . (We can also consider the case where players of the same type may have different policies, but let's keep it simple for now.) In the thermodynamic limit, the population is described as a distribution over histories, which now are allowed to be of variable length: . For each assignment of policies to player types, we get dynamics where . So, as opposed to immortal population games, mortal population games naturally give rise to dynamical systems.

If we consider only the age distribution, then its evolution doesn't depend on and it always converges to the unique fixed point distribution . Therefore it is natural to restrict the dynamics to the subspace of that corresponds to the age distribution . We denote it .

Does the dynamics have fixed points? can be regarded as a subspace of . The later is compact (in the product topology) by Tychonoff's theorem and Polish, but is not closed. So, w.r.t. the weak topology on probability measure spaces, is also compact but isn't. However, it is easy to see that is closed in and therefore compact. It may also be regarded as a convex subset of an appropriate Banach space (the dual of the space of Lipschitz functions on some metrization of ). Moreover, it is easy to see is continuous (for populations that are close in the Kantorovich-Rubinstein metric, only the old players may have very different distributions, but old players are a small fraction of the population so their effect on the next round is small). By the Schauder fixed-point theorem, it follows that has a fixed point.

What are the fixed points like? Of course it depends on . In a fixed point, every player observes a sequence of IID plays in all of eir games. Therefore, if satisfies the (very mild!) learning-theoretic desideratum that, upon observing an IID sequence, it converges to optimal response in the limit, then, in the same limit, fixed points are Nash equilibria. This works even for extremely simple learning algorithms, such as "assume the plays in the next game will be sampled from a random past game", and it works for any Bayesian or "quasi-Bayesian" (i.e. using incomplete/fuzzy models [AF · GW]) agent that includes all IID processes in its prior.

This raises a range of interesting questions:

  • Are any/all of the fixed points attractors?
  • Does convergence to a fixed point occur for all or at least almost all initial conditions?
  • Do all Nash equilibria correspond to fixed points?
  • Do stronger game theoretic solution concepts (e.g. proper equilibria) have corresponding dynamical properties?

Mortal population games are obviously reminiscent of evolutionary game theory. However, there are substantial differences. In mortal population games, the game doesn't have to be symmetric, we consider a single policy rather than many competing policies, the policies learn from experience instead of corresponding to fixed strategies, and mortality rate doesn't depend on the reward. In evolutionary game theory, convergence usually cannot be guaranteed. For example, in the rock-scissors-paper game, the population may cycle among the different strategies. On the other hand, in mortal population games, if the game is two-player zero-sum (which includes rock-paper-scissors), and the policy is quasi-Bayesian with appropriate prior, convergence is guaranteed. This is because each player can easily learn to guarantee maximin payoff. Continuity arguments probably imply that at least for small perturbations of zero-sum, there will still be convergence. This leads to some hope that convergence can be guaranteed even in general games, or at least under some relatively mild conditions.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-01-05T16:54:10.813Z · LW(p) · GW(p)

Some thoughts about embedded agency.

From a learning-theoretic perspective, we can reformulate the problem of embedded agency as follows: What kind of agent, and in what conditions, can effectively plan for events after its own death? For example, Alice bequeaths eir fortune to eir children, since ey want them be happy even when Alice emself is no longer alive. Here, "death" can be understood to include modification, since modification is effectively destroying an agent and replacing it by different agent[1]. For example, Clippy 1.0 is an AI that values paperclips. Alice disabled Clippy 1.0 and reprogrammed it to value staples before running it again. Then, Clippy 2.0 can be considered to be a new, different agent.

First, in order to meaningfully plan for death, the agent's reward function has to be defined in terms of something different than its direct perceptions. Indeed, by definition the agent no longer perceives anything after death. Instrumental reward functions [AF · GW] are somewhat relevant but still don't give the right object, since the reward is still tied to the agent's actions and observations. Therefore, we will consider reward functions defined in terms of some fixed ontology of the external world. Formally, such an ontology can be an incomplete[2] Markov chain, the reward function being a function of the state. Examples:

  • The Markov chain is a representation of known physics (or some sector of known physics). The reward corresponds to the total mass of diamond in the world. To make this example work, we only need enough physics to be able to define diamonds. For example, we can make do with quantum electrodynamics + classical gravity and have the Knightian uncertainty account for all nuclear and high-energy phenomena.

  • The Markov chain is a representation of people and social interactions. The reward correspond to concepts like "happiness" or "friendship" et cetera. Everything that falls outside the domain of human interactions is accounted by Knightian uncertainty.

  • The Markov chain is Botworld with some of the rules left unspecified. The reward is the total number of a particular type of item.

Now we need to somehow connect the agent to the ontology. Essentially we need a way of drawing Cartesian boundaries inside the (a priori non-Cartesian) world. We can accomplish this by specifying a function that assigns an observation and projected action to every state out of some subset of states. Entering this subset corresponds to agent creation, and leaving it corresponds to agent destruction. For example, we can take the ontology to be Botworld + marked robot and the observations and actions be the observations and actions of that robot. If we don't want marking a particular robot as part of the ontology, we can use a more complicated definition of Cartesian boundary that specifies a set of agents at each state plus the data needed to track these agents across time (in this case, the observation and action depend to some extent on the history and not only the current state). I will leave out the details for now.

Finally, we need to define the prior. To do this, we start by choosing some prior over refinements of the ontology. By "refinement", I mean removing part of the Knightian uncertainty, i.e. considering incomplete hypotheses which are subsets of the "ontological belief". For example, if the ontology is underspecified Botworld, the hypotheses will specify some of what was left underspecified. Given such a "objective" prior and a Cartesian boundary, we can construct a "subjective" prior for the corresponding agent. We transform each hypothesis via postulating that taking an action that differs from the projected action leads to "Nirvana [AF(p) · GW(p)]" state. Alternatively, we can allow for stochastic action selection and use the gambler construction [AF(p) · GW(p)].

Does this framework guarantee effective planning for death? A positive answer would correspond to some kind of learnability result (regret bound). To get learnability, will first need that the reward is either directly on indirectly observable. By "indirectly observable" I mean something like with semi-instrumental reward functions, but accounting for agent mortality. I am not ready to formulate the precise condition atm. Second, we need to consider an asymptotic in which the agent is long lived (in addition to time discount being long-term), otherwise it won't have enough time to learn. Third (this is the trickiest part), we need the Cartesian boundary to flow with the asymptotic as well, making the agent "unspecial". For example, consider Botworld with some kind of simplicity prior. If I am a robot born at cell zero and time zero, then my death is an event of low description complexity. It is impossible to be confident about what happens after such a simple event, since there will always be competing hypotheses with different predictions and a probability that is only lower by a factor of . On the other hand, if I am a robot born at cell 2439495 at time 9653302 then it would be surprising if the outcome of my death would be qualitatively different from the outcome of the death of any other robot I observed. Finding some natural, rigorous and general way to formalize this condition is a very interesting problem. Of course, even without learnability we can strive for Bayes-optimality or some approximation thereof [AF(p) · GW(p)]. But, it is still important to prove learnability under certain conditions to test that this framework truly models rational reasoning about death.

Additionally, there is an intriguing connection between some of these ideas and UDT, if we consider TRL agents. Specifically, a TRL agent can have a reward function that is defined in terms of computations, exactly like UDT is often conceived. For example, we can consider an agent whose reward is defined in terms of a simulation of Botworld, or in terms of taking expected value over a simplicity prior over many versions of Botworld. Such an agent would be searching for copies of itself inside the computations it cares about, which may also be regarded as a form of "embeddedness". It seems like this can be naturally considered a special case of the previous construction, if we allow the "ontological belief" to include beliefs pertaining to computations.

  1. Unless it's some kind of modification that we treat explicitly in our model of the agent, for example a TRL [AF(p) · GW(p)] agent reprogramming its own envelope. ↩︎

  2. "Incomplete" in the sense of Knightian uncertainty, like in quasi-Bayesian RL [AF(p) · GW(p)]. ↩︎

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-03-24T14:08:33.763Z · LW(p) · GW(p)

Learning theory distinguishes between two types of settings: realizable and agnostic (non-realizable). In a realizable setting, we assume that there is a hypothesis in our hypothesis class that describes the real environment perfectly. We are then concerned with the sample complexity and computational complexity of learning the correct hypothesis. In an agnostic setting, we make no such assumption. We therefore consider the complexity of learning the best approximation of the real environment. (Or, the best reward achievable by some space of policies.)

In offline learning and certain varieties of online learning, the agnostic setting is well-understood. However, in more general situations it is poorly understood. The only agnostic result for long-term forecasting that I know is Shalizi 2009, however it relies on ergodicity assumptions that might be too strong. I know of no agnostic result for reinforcement learning.

Quasi-Bayesianism was invented to circumvent the problem. Instead of considering the agnostic setting, we consider a "quasi-realizable" setting: there might be no perfect description of the environment in the hypothesis class, but there are some incomplete descriptions. But, so far I haven't studied quasi-Bayesian learning algorithms much, so how do we know it is actually easier than the agnostic setting? Here is a simple example to demonstrate that it is.

Consider a multi-armed bandit, where the arm space is . First, consider the follow realizable setting: the reward is a deterministic function which is known to be a polynomial of degree at most. In this setting, learning is fairly easy: it is enough to sample arms in order to recover the reward function and find the optimal arm. It is a special case of the general observation that learning is tractable when the hypothesis space is low-dimensional in the appropriate sense.

Now, consider a closely related agnostic setting. We can still assume the reward function is deterministic, but nothing is known about its shape and we are still expected to find the optimal arm. The arms form a low-dimensional space (one-dimensional actually) but this helps little. It is impossible to predict anything about any arm except those we already tested, and guaranteeing convergence to the optimal arm is therefore also impossible.

Finally, consider the following quasi-realizable setting: each incomplete hypothesis in our class states that the reward function is lower-bounded by a particular polynomial of degree at most. Our algorithm needs to converge to a reward which is at least the maximum of maxima of correct lower bounds. So, the desideratum is weaker than in the agnostic case, but we still impose no hard constraint on the reward function. In this setting, we can use the following algorithm. On each step, fit the most optimistic lower bound to those arms that were already sampled, find its maximum and sample this arm next. I haven't derived the convergence rate, but it seems probable the algorithm will converge rapidly (for low ). This is likely to be a special case of some general result on quasi-Bayesian learning with low-dimensional priors.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-21T12:44:05.142Z · LW(p) · GW(p)

This is preliminary description of what I dubbed Dialogic Reinforcement Learning (credit for the name goes to tumblr user @di--es---can-ic-ul-ar--es): the alignment scheme I currently find most promising.

It seems that the natural formal criterion for alignment (or at least the main criterion) is having a "subjective regret bound": that is, the AI has to converge (in the long term planning limit, limit) to achieving optimal expected user!utility with respect to the knowledge state of the user. In order to achieve this, we need to establish a communication protocol between the AI and the user that will allow transmitting this knowledge state to the AI (including knowledge about the user's values). Dialogic RL attacks this problem in the manner which seems the most straightforward and powerful: allowing the AI to ask the user questions in some highly expressive formal language, which we will denote .

allows making formal statements about a formal model of the world, as seen from the AI's perspective. includes such elements as observations, actions, rewards and corruption. That is, reflects (i) the dynamics of the environment (ii) the values of the user (iii) processes that either manipulate the user, or damage the ability to obtain reliable information from the user. Here, we can use different models of values: a traditional "perceptible" reward function, an instrumental reward function [AF · GW], a semi-instrumental reward functions, dynamically-inconsistent rewards [AF(p) · GW(p)], rewards with Knightian uncertainty etc. Moreover, the setup is self-referential in the sense that, also reflects the question-answer interface and the user's behavior.

A single question can consist, for example, of asking for the probability of some sentence in or the expected value of some expression of numerical type in . However, in order to address important features of the world, such questions have to be very complex. It is infeasible to demand that the user understands such complex formal questions unaided. Therefore, the AI always produces a formal question together with a natural language () annotation . This annotation has to explain the question in human understandable terms, and also convince the user that is indeed an accurate natural language rendering of . The user's feedback then consists of (i) accepting/rejecting/grading the annotation (ii) answering the question if the annotation is correct and the user can produce the answer. Making this efficient requires a process of iteratively constructing a correspondence between and , i.e effectively building a new shared language between the user and the AI. We can imagine concepts defined in and explained in that serve to define further, more complex, concepts, where at each stage the previous generation of concepts can be assumed given and mutually understandable. In addition to such intensional definitions we may also allow extensional definitions, as long as the generalization is assumed to be via some given function space that is relatively restricted (e.g. doesn't admit subagents). There seem to be some strong connections between the subproblem of designing the annotation system and the field of transparency in AI.

The first major concern that arises at this point is, questions can serve as an attack vector. This is addressed by quantilization. The key assumption is: it requires much less optimization power to produce some useful question than to produce a malicious question. Under this assumption, the quantilization parameter can be chosen to make the question interface safe but still effective. Over time, the agent accumulates knowledge about corruption dynamics that allows it to steer even further away from malicious questions while making the choice of questions even more effective. For the attack vector of deceitful annotations, we can improve safety using the debate approach [AF(p) · GW(p)], i.e. having the agent to produce additional natural language text that attempts to refute the validity of the annotation.

Of course, in addition to the question interface, the physical interface (direct interaction with environment) is also an attack vector (like in any RL system). There, safety is initially guaranteed by following a baseline policy (which can be something like "do nothing" or human imitation). Later, the agent starts deviating from the baseline policy while staying safe, by leveraging the knowledge it previously gained through both the question and the physical interface. Besides being safe, the algorithm also need to be effective, and for this it has to (in particular) find the learning strategy that optimally combines gaining knowledge through the question interface and gaining knowledge through autonomous exploration.

Crucially, we want our assumptions about user competence to be weak. This means that, the user can produce answers that are (i) incomplete (just refuse to answer) (ii) fickle (change eir answers) and (iii) inconsistent (contradictory answers). We address (i) by either assuming that the answerable questions are sufficient or requiring a weaker regret bound where the reference agents knows all obtainable answers rather than knowing the full knowledge state they refer to. We address (ii) by believing later answers over earlier answers and via the commitment mechanism (see below). We address (iii) by explaining the contradictions to the user and asking for their resolution. In addition to all that, the AI can predict the answers instead of actually asking (i.e. the user's knowledge state is also assumed to be regular to some extent). The commitment mechanism is a key tool for achieving optimal trade-off between allowing the user more time to think vs. acting quickly enough to address external dangers, while keeping the user informed of the consequences. It works by having the AI ask the user for a committed answer at the point of time when the AI has to commit to an irreversible course of action (and not much earlier), based on this particular answer. The AI provides the user with a a description of the Pareto frontier for the different possible answers. Moreover, even committed answers can be changed later. In this case, the algorithm cannot guarantee global optimality but it should still guarantee "subgame perfection": i.e., whatever irreversible mistakes were made, the AI recovers as best as possible.

In order to improve the user's ability to produce answers and stay informed about the AI's strategy, we introduce another interface through which the user can ask questions from the AI. In this direction, the user asks the question in and the AI both translates it to and provides a justification (as well as a refutation) of the translation, again employing quantilization. The user can then accept or reject the translation. If the translation is rejected, ey may require the AI to try again. If it is accepted, the AI produces an answer to the best of its ability. In general, it may be that producing an answer requires compiling a formal proof in which case the AI may or may not succeed. Here, there is concern about the scenario where (i) the user asks a question about a possible future (ii) the AI answers with a detailed description of the future (iii) as a result, the user is exposed to infohazards (sources of corruption) within this future. To address this, we need to either restrict the interface to small volumes of data, or shape the prior s.t. the AI can on its own realize the inherent danger. In the latter approach, the AI can refuse to answer or provide a "censored" answer while pointing out the presence of a potential infohazard.

Finally, the subjective regret bound approach might seem to impose a strong cap on capability: if the AI follows a policy optimal w.r.t. the user's knowledge state, then the limited computational abilities of the user might prevent the AI from creating models of the world that are more detailed. This can be addressed in a Turing Reinforcement Learning [AF(p) · GW(p)] setting, by allowing the user's knowledge state to refer to arbitrary computations. The user can then be incapable of executing those computations, but the AI might be more able to do so.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-20T14:18:54.689Z · LW(p) · GW(p)

I gave a talk on Dialogic Reinforcement Learning in the AI Safety Discussion Day, and there is a recording.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-18T13:48:47.486Z · LW(p) · GW(p)

A variant of Dialogic RL with improved corrigibility. Suppose that the AI's prior allows a small probability for "universe W" whose semantics are, roughly speaking, "all my assumptions are wrong, need to shut down immediately". In other words, this is a universe where all our prior shaping is replaced by the single axiom that shutting down is much higher utility than anything else. Moreover, we add into the prior that assumption that the formal question "W?" is understood perfectly by the user even without any annotation. This means that, whenever the AI assigns a higher-than-threshold probability to the user answering "yes" if asked "W?" at any uncorrupt point in the future, the AI will shutdown immediately. We should also shape the prior s.t. corrupt futures also favor shutdown: this is reasonable in itself, but will also ensure that the AI won't arrive at believing too many futures to be corrupt and thereby avoid the imperative to shutdown as response to a confirmation of W.

Now, this won't help if the user only resolves to confirm W after something catastrophic already occurred, such as the AI releasing malign subagents into the wild. But, something of the sort is true for any corrigibility scheme: corrigibility is about allowing the user to make changes in the AI on eir own initiative, which can always be too late. This method doesn't ensure safety in itself, just hardens a system that is supposed to be already close to safe.

It would be nice if we could replace "shutdown" by "undo everything you did and then shutdown" but that gets us into thorny specifications issues. Perhaps it's possible to tackle those issues by one of the approaches to "low impact".

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-28T18:20:22.446Z · LW(p) · GW(p)

Universe W should still be governed by a simplicity prior. This means that whenever the agent detects a salient pattern that contradicts the assumptions of its prior shaping, the probability of W increases leading to shutdown. This serves as an additional "sanity test" precaution.

comment by Gurkenglas · 2019-10-21T15:08:00.147Z · LW(p) · GW(p)

This design is made of so many parts! It might benefit from a proof that it is the universal answer to a formal question, which I expect to seem less overly complex.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-21T16:46:29.686Z · LW(p) · GW(p)

I am not sure. AI alignment seems to touch on many different aspects of the world, and it is not obvious that it can be reduced to assumptions that are extremely simple and natural. Or, if it can be reduced that way, then it might require a theory that on some level explains human civilization, its evolution and and its influence on the world (even if only on a fairly abstract level). I will share some thoughts how the various assumptions can be reduced another step back, but proceeding to reduce all of them to a simple core seems like a challenging research programme.

Most of the parts of this design can be regarded as reflecting particular assumptions we make about the user as an agent.

The core idea of having a dialogue comes from modeling the user as a "linguistic agent". Such agents may be viewed as nodes in a distributed AI system, but where each node has different objectives. It is an interesting philosophical question whether this assumption is necessary for value learning. It currently seems plausible to me that only for linguistic agents "values" are truly well-defined, or at least sufficiently well-defined to extrapolate them outside the trajectory that the agent follows on its own.

The need to quantilize, debate and censor infohazards comes from the assumption that the user can be manipulated (there is some small fraction of possible inputs that invalidate the usual assumptions about the user's behavior). Specifically debate might be possible to justify by some kind of Bayesian framework where every argument is a piece of evidence, and providing biased arguments is like providing selective evidence.

The need to deal with "incoherent" answers and the commitment mechanism comes from the assumption the user has limited access to its own knowledge state (including its own reward function). Perhaps we can formalize it further by modeling the user as a learning algorithm with some intrinsic source of information. Perhaps we can even explain why such agents are natural in the "distributed AI" framework, or by some evolutionary argument.

The need to translate between formal language and natural languages come from, not knowing the "communication protocol" of the "nodes". Formalizing this idea further requires some more detailed model of what "natural language" is, which might be possible via multi-agent learning theory.

Finally, the need to start from a baseline policy (and also the need to quantilize) comes from the assumption that the environment is not entirely secure. So that's an assumption about the current state of the world, rather than about the user. Perhaps, we can make formal the argument that this state of the world (short-term stable, long-term dangerous) is to be expected when agents populated it for a long time.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-05-06T19:34:30.109Z · LW(p) · GW(p)

This idea was inspired by a correspondence with Adam Shimi.

It seem very interesting and important to understand to what extent a purely "behaviorist" view on goal-directed intelligence is viable. That is, given a certain behavior (policy), is it possible to tell whether the behavior is goal-directed and what are its goals, without any additional information?

Consider a general reinforcement learning settings: we have a set of actions , a set of observations , a policy is a mapping , a reward function is a mapping , the utility function is a time discounted sum of rewards. (Alternatively, we could use instrumental reward functions [AF · GW].)

The simplest attempt at defining "goal-directed intelligence" is requiring that the policy in question is optimal for some prior and utility function. However, this condition is vacuous: the reward function can artificially reward only behavior that follows , or the prior can believe that behavior not according to leads to some terrible outcome.

The next natural attempt is bounding the description complexity of the prior and reward function, in order to avoid priors and reward functions that are "contrived". However, description complexity is only naturally well-defined up to an additive constant. So, if we want to have a crisp concept, we need to consider an asymptotic in which the complexity of something goes to infinity. Indeed, it seems natural to ask that the complexity of the policy should be much higher than the complexity of the prior and the reward function: in this case we can say that the "intentional stance" is an efficient description. However, this doesn't make sense with description complexity: the description "optimal policy for and " is of size ( stands for "description complexity of ").

To salvage this idea, we need to take not only description complexity but also computational complexity into account. [EDIT: I was wrong, and we can get a well-defined concept in the unbounded setting too, see child comment [LW(p) · GW(p)]. The bounded concept is still interesting.] For the intentional stance to be non-vacuous we need to demand that the policy does some "hard work" in order to be optimal. Let's make it formal. Consider any function of the type where and are some finite alphabets. Then, we can try to represent it by a probabilistic automaton , where is the finite set space, is the transition kernel, and we're feeding symbols into the automaton one by one. Moreover, can be represented as a boolean circuit and this circuit can be the output of some program executed by some fixed universal Turing machine. We can associate with this object 5 complexity parameters:

  • The description complexity, which is the length of .
  • The computation time complexity, which is the size of .
  • The computation space complexity, which is the maximum between the depth of and .
  • The precomputation time complexity, which is the time it takes to run.
  • The precomputation space complexity, which is the space needs to run.

It is then natural to form a single complexity measure by applying a logarithm to the times and taking a linear combination of all 5 (we apply a logarithm so that a brute force search over bits is roughly equivalent to hard-coding bits). The coefficients in this combination represent the "prices" of the various resources (but we should probably fix the price of description complexity to be 1). Of course not all coefficients must be non-vanishing, it's just that I prefer to keep maximal generality for now. We will denote this complexity measure .

We can use such automatons to represent policies, finite POMDP environments and reward functions (ofc not any policy or reward function, but any that can be computed on a machine with finite space). In the case of policies, the computation time/space complexity can be regarded as the time/space cost of applying the "trained" algorithm, whereas the precomputation time/space complexity can be regarded as the time/space cost of training. If we wish, we can also think of the boolean circuit as a recurrent neural network.

We can also use to define a prior , by ranging over programs that output a valid POMDP and assigning probability proportional to to each instance. (Assuming that the environment has a finite state space might seem restrictive, but becomes quite reasonable if we use a quasi-Bayesian setting with quasi-POMDPs that are not meant to be complete descriptions of the environment; for now we won't go into details about this.)

Now, return to our policy . Given , we define that " has goal-directed intelligence (at least) " when there is a suitable prior and utility function s.t. for any policy , if then . When (i.e. no finite automaton can match the expected utility of ; in particular, this implies is optimal since any policy can be approximated by a finite automaton), we say that is "perfectly goal-directed". Here, serves as a way to measure the complexity of , which also ensures is non-dogmatic in some rather strong sense.

With this definition we cannot "cheat" by encoding the policy into the prior or into the utility function, since that would allow no complexity difference. Therefore this notion seems like a non-trivial requirement on the policy. On the other hand, this requirement does hold sometimes, because solving the optimization problem can be much more computationally costly than just evaluating the utility function or sampling the prior.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-05-09T10:20:48.714Z · LW(p) · GW(p)

Actually, as opposed to what I claimed before, we don't need computational complexity bounds for this definition to make sense. This is because the Solomonoff prior is made of computable hypotheses but is uncomputable itself.

Given , we define that " has (unbounded) goal-directed intelligence (at least) " when there is a prior and utility function s.t. for any policy , if then . Here, is the Solomonoff prior and is Kolmogorov complexity. When (i.e. no computable policy can match the expected utility of ; in particular, this implies is optimal since any policy can be approximated by a computable policy), we say that is "perfectly (unbounded) goal-directed".

Compare this notion to the Legg-Hutter intelligence measure. The LH measure depends on the choice of UTM in radical ways. In fact, for some UTMs, AIXI (which is the maximum of the LH measure) becomes computable or even really stupid. For example, it can always keep taking the same action because of the fear that taking any other action leads to an inescapable "hell" state. On the other hand, goal-directed intelligence differs only by between UTMs, just like Kolmogorov complexity. A perfectly unbounded goal-directed policy has to be uncomputable, and the notion of which policies are such doesn't depend on the UTM at all.

I think that it's also possible to prove that intelligence is rare, in the sense that, for any computable stochastic policy, if we regard it as a probability measure over deterministic policies, then for any there is s.t. the probability to get intelligence at least is smaller than .

Also interesting is that, for bounded goal-directed intelligence, increasing the prices can only decrease intelligence by , and a policy that is perfectly goal-directed w.r.t. lower prices is also such w.r.t. higher prices (I think). In particular, a perfectly unbounded goal-directed policy is perfectly goal-directed for any price vector. Informally speaking, an agent that is very smart relatively to a context with cheap computational resources is still very smart relatively to a context where they are expensive, which makes intuitive sense.

If we choose just one computational resource, we can speak of the minimal price for which a given policy is perfectly goal-directed, which is another way to measure intelligence with a more restricted domain. Curiously, our bounded Solomonoff-like prior has the shape of a Maxwell-Boltzmann distribution in which the prices are thermodynamic parameters. Perhaps we can regard the minimal price as the point of a phase transition.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-21T14:15:25.741Z · LW(p) · GW(p)

Some problems to work on regarding goal-directed intelligence. Conjecture 5 is especially important for deconfusing basic questions in alignment, as it stands in opposition to Stuart Armstrong's thesis about the impossibility to deduce preferences from behavior alone.

  1. Conjecture. Informally: It is unlikely to produce intelligence by chance. Formally: Denote the space of deterministic policies, and consider some . Suppose is equivalent to a stochastic policy . Then, .

  2. Find an "intelligence hierarchy theorem". That is, find an increasing sequence s.t. for every , there is a policy with goal-directed intelligence in (no more and no less).

  3. What is the computational complexity of evaluating given (i) oracle access to the policy or (ii) description of the policy as a program or automaton?

  4. What is the computational complexity of producing a policy with given ?

  5. Conjecture. Informally: Intelligent agents have well defined priors and utility functions. Formally: For every with and , and every , there exists s.t. for every policy with intelligence at least w.r.t. , and every s.t. has intelligence at least w.r.t. them, any optimal policies for and respectively satisfy .

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-26T17:18:51.954Z · LW(p) · GW(p)

Much of the orthodox LessWrongian approach to rationality (as it is expounded in Yudkowsky's Sequences and onwards) is grounded in Bayesian probability theory. However, I now realize that pure Bayesianism is wrong, instead the right thing is quasi-Bayesianism [LW(p) · GW(p)]. This leads me to ask, what are the implications of quasi-Bayesianism on human rationality? What are the right replacements for (the Bayesian approach to) bets, calibration, proper scoring rules et cetera? Does quasi-Bayesianism clarify important confusing issues in regular Bayesianism such as the proper use of inside and outside view? Is there rigorous justification to the intuition that we should have more Knightian uncertainty about questions with less empirical evidence? Does any of it influence various effective altruism calculations in surprising ways? What common LessWrongian wisdom does it undermine, if any?

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-30T23:03:22.324Z · LW(p) · GW(p)

In Hanson’s futarchy, the utility function of the state is determined by voting but the actual policy is determined by a prediction market. But, voting incentivizes misrepresenting your values to get a larger share of the pie. So, shouldn’t it be something like the VCG mechanism instead?

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-11T16:56:01.541Z · LW(p) · GW(p)

In the past I considered the learning-theoretic approach to AI theory [AF · GW] as somewhat opposed to the formal logic approach popular in MIRI [AF · GW] (see also discussion [AF(p) · GW(p)]):

  • Learning theory starts from formulating natural desiderata for agents, whereas "logic-AI" usually starts from postulating a logic-based model of the agent ad hoc.
  • Learning theory naturally allows analyzing computational complexity whereas logic-AI often uses models that are either clearly intractable or even clearly incomputable from the onset.
  • Learning theory focuses on objects that are observable or finite/constructive, whereas logic-AI often considers objects that unobservable, infinite and unconstructive (which I consider to be a philosophical error).
  • Learning theory emphasizes induction whereas logic-AI emphasizes deduction.

However, recently I noticed that quasi-Bayesian reinforcement learning [AF(p) · GW(p)] and Turing reinforcement learning [AF(p) · GW(p)] have very suggestive parallels to logic-AI. TRL agents have beliefs about computations they can run on the envelope: these are essentially beliefs about mathematical facts (but, we only consider computable facts and computational complexity plays some role there). QBRL agents reason in terms of hypotheses that have logical relationships between them: the order on functions corresponds to implication, taking the minimum of two functions corresponds to logical "and", taking the concave hull of two functions corresponds to logical "or". (but, there is no "not", so maybe it's a sort of intuitionist logic?) In fact, fuzzy beliefs form a continuous dcpo [AF(p) · GW(p)], and considering some reasonable classes of hypotheses probably leads to algebraic dcpo-s, suggesting a strong connection with domain theory (also, it seems like considering beliefs within different ontologies leads to a functor from some geometric category (the category of ontologies) to dcpo-s).

These parallels suggest that the learning theory of QBRL/TRL will involve some form of deductive reasoning and some type of logic. But, this doesn't mean that QBRL/TRL is redundant w.r.t. logic AI! In fact, QBRL/TRL might lead us to discover exactly which type of logic do intelligent agents need and what is the role logic should play in the theory and inside the algorithms (instead of trying to guess and impose the answer ad hoc, which IMO did not work very well so far). Moreover, I think that the type of logic we are going to get will be something finitist/constructivist, and in particular this is probably how Goedelian paradoxes will be avoid. However, the details remain to be seen.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-26T13:04:24.146Z · LW(p) · GW(p)

I recently realized that the formalism of incomplete models [AF · GW] provides a rather natural solution to all decision theory problems involving "Omega" (something that predicts the agent's decisions). An incomplete hypothesis may be thought of a zero-sum game between the agent and an imaginary opponent (we will call the opponent "Murphy" as in Murphy's law). If we assume that the agent cannot randomize against Omega, we need to use the deterministic version of the formalism. That is, an agent that learns an incomplete hypothesis converges to the corresponding maximin value in pure strategies. (The stochastic version can be regarded as a special case of the deterministic version where the agent has access to an external random number generator that is hidden from the rest of the environment according to the hypothesis.) To every decision problem, we can now correspond an incomplete hypothesis as follows. Every time Omega makes a prediction about the agent's future action in some counterfactual, we have Murphy make a guess instead. This guess cannot be directly observed by the agent. If the relevant counterfactual is realized, then the agent's action renders the guess false or true. If the guess is false, the agent receives infinite (or, sufficiently large) reward. If the guess is true, everything proceeds as usual. The maximin value then corresponds to the scenario where the guess is true and the agent behaves as if its action controls the guess. (Which is exactly what FDT and its variants try to achieve.)

For example, consider (repeated) counterfactual mugging. The incomplete hypothesis is a partially observable stochastic game (between the agent and Murphy), with the following states:

  • : initial state. Murphy has two actions: (guess the agent will pay), transitioning to and (guess the agent won't pay) transitioning to . (Reward = )
  • : Murphy guessed the agent will pay. Transitions to or with probability to each (the coin flip). (Reward = )
  • : Murphy guessed the agent won't pay. Transitions to or with probability to each (the coin flip). (Reward = )
  • : Agent receives the prize. Transitions to . (Reward = )
  • : Agent is asked for payment. Agent has two actions: (pay) transitioning to and (don't pay) transitioning to . (Reward = )
  • : Agent receives nothing. Transitions to . (Reward = )
  • : Agent is asked for payment. Agent has two actions: (pay) transitioning to and (don't pay) transitioning to . (Reward = )
  • : Murphy's guess remained untested. Transitions to . (Reward = )
  • : Murphy's guess was right, agent paid. Transitions to . (Reward = )
  • : Murphy's guess was right, agent didn't pay. Transitions to . (Reward = )
  • : Murphy's guess was wrong, agent paid. Transitions to . (Reward = )
  • : Murphy's guess was wrong, agent didn't pay. Transitions to . (Reward = )

The only percepts the agent receives are (i) the reward and (ii) whether it is asked for payment or not. The agent's maximin policy is paying, since it guarantees an expected reward of per round.

We can generalize this to an imperfect predictor (a predictor that sometimes makes mistakes), by using the same construction but adding noise to Murphy's guess for purposes other than the guess's correctness. Apparently, We can also generalize to the variant where the agent can randomize against Omega and Omega decides based on its predictions of the probabilities. This, however, is more complicated. In this variant there is no binary notion of "right" and "wrong" guess. Instead, we need to apply some statistical test to the guesses and compare it against a threshold. We can then consider a family of hypotheses with different thresholds, such that (i) with probability , for all but some finite number of thresholds, accurate guesses would never be judged wrong by the test (ii) with probability , consistently inaccurate guesses will be judged wrong by the test, with any threshold.

The same construction applies to logical counterfactual mugging, because the agent cannot distinguish between random and pseudorandom (by definition of pseudorandom). In TRL [AF(p) · GW(p)] there would also be some family of programs the agent could execute s.t., according the hypothesis, their outputs are determined by the same "coin flips" as the offer to pay. However, this doesn't change the optimal strategy: the "logical time of precommitment" is determined by the computing power of the "core" RL agent, without the computer "envelope".

comment by Nisan · 2019-11-07T22:28:27.972Z · LW(p) · GW(p)

My takeaway from this is that if we're doing policy selection in an environment that contains predictors, instead of applying the counterfactual belief that the predictor is always right, we can assume that we get rewarded if the predictor is wrong, and then take maximin.

How would you handle Agent Simulates Predictor? Is that what TRL is for?

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-08T16:34:54.316Z · LW(p) · GW(p)

That's about right. The key point is, "applying the counterfactual belief that the predictor is always right" is not really well-defined (that's why people have been struggling with TDT/UDT/FDT for so long) while the thing I'm doing is perfectly well-defined. I describe agents that are able to learn which predictors exist in their environment and respond rationally ("rationally" according to the FDT philosophy).

TRL is for many things to do with rational use of computational resources, such as (i) doing multi-level modelling [AF(p) · GW(p)] in order to make optimal use of "thinking time" and "interacting with environment time" (i.e. simultaneously optimize sample and computational complexity) (ii) recursive self-improvement (iii) defending from non-Cartesian daemons (iv) preventing thought crimes. But, yes, it also provides a solution to ASP [AF(p) · GW(p)]. TRL agents can learn whether it's better to be predictable or predicting.

comment by Chris_Leong · 2019-12-05T15:18:55.692Z · LW(p) · GW(p)

"The key point is, "applying the counterfactual belief that the predictor is always right" is not really well-defined" - What do you mean here?

I'm curious whether you're referring to the same as or similar to the issue I was referencing in Counterfactuals for Perfect Predictors [LW · GW]. The TLDR is that I was worried that it would be inconsistent for an agent that never pays in Parfait's Hitchhiker to end up in town if the predictor is perfect, so that it wouldn't actually be well-defined what the predictor was predicting. And the way I ended up resolving this was by imagining it as an agent that takes input and asking what it would output if given that inconsistent input. But not sure if you were referencing this kind of concern or something else.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-05T15:46:54.665Z · LW(p) · GW(p)

It is not a mere "concern", it's the crux of problem really. What people in the AI alignment community have been trying to do is, starting with some factual and "objective" description of the universe (such a program or a mathematical formula) and deriving counterfactuals. The way it's supposed to work is, the agent needs to locate all copies of itself or things "logically correlated" with itself (whatever that means) in the program, and imagine it is controlling this part. But a rigorous definition of this that solves all standard decision theoretic scenarios was never found.

Instead of doing that, I suggest a solution of different nature. In quasi-Bayesian RL, the agent never arrives at a factual and objective description of the universe. Instead, it arrives at a subjective description which already includes counterfactuals. I then proceed to show that, in Newcomb-like scenarios, such agents receive optimal expected utility (i.e. the same expected utility promised by UDT).

comment by Chris_Leong · 2019-12-05T16:01:32.781Z · LW(p) · GW(p)

Yeah, I agree that the objective descriptions can leave out vital information, such as how the information you know was acquired, which seems important for determining the counterfactuals.

comment by cousin_it · 2019-11-13T11:10:35.136Z · LW(p) · GW(p)

But in Newcomb's problem, the agent's reward in case of wrong prediction is already defined. For example, if the agent one-boxes but the predictor predicted two-boxing, the reward should be zero. If you change that to +infinity, aren't you open to the charge of formalizing the wrong problem?

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-13T13:23:55.781Z · LW(p) · GW(p)

The point is, if you put this "quasi-Bayesian" agent into an iterated Newcomb-like problem, it will learn to get the maximal reward (i.e. the reward associated with FDT). So, if you're judging it from the side, you will have to concede it behaves rationally, regardless of its internal representation of reality.

Philosophically, my point of view is, it is an error to think that counterfactuals have objective, observer-independent, meaning. Instead, we can talk about some sort of consistency conditions between the different points of view. From the agent's point of view, it would reach Nirvana if it dodged the predictor. From Omega's point of view, if Omega two-boxed and the agent one-boxed, the agent's reward would be zero (and the agent would learn its beliefs were wrong). From a third-person point of view, the counterfactual "Omega makes an error of prediction" is ill-defined, it's conditioning on an event of probability 0.

comment by cousin_it · 2019-11-13T16:16:24.278Z · LW(p) · GW(p)

Yeah, I think I can make peace with that. Another way to think of it is that we can keep the reward structure of the original Newcomb's problem, but instead of saying "Omega is almost always right" we add another person Bob (maybe the mad scientist who built Omega) who's willing to pay you a billion dollars if you prove Omega wrong. Then minimaxing indeed leads to one-boxing. Though I guess the remaining question is why minimaxing is the right thing to do. And if randomizing is allowed, the idea of Omega predicting how you'll randomize seems a bit dodgy as well.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-30T13:06:02.593Z · LW(p) · GW(p)

Another explanation why maximin is a natural decision rule: when we apply maximin to fuzzy beliefs [AF(p) · GW(p)], the requirement to learn a particular class of fuzzy hypotheses is a very general way to formulate asymptotic performance desiderata for RL agents. So general that it seems to cover more or less anything you might want. Indeed, the definition directly leads to capturing any desideratum of the form

Here, doesn't have to be concave: the concavity condition in the definition of fuzzy beliefs is there because we can always assume it without loss of generality. This is because the left hand side in linear in so any that satisfies this will also satisfy it for the concave hull of .

What if instead of maximin we want to apply the minimax-regret decision rule? Then the desideratum is

But, it has the same form! Therefore we can consider it as a special case of the applying maximin (more precisely, it requires allowing the fuzzy belief to depend on , but this is not a problem for the basics of the formalism).

What if we want our policy to be at least as good as some fixed policy ? Then the desideratum is

It still has the same form!

Moreover, the predictor/Nirvana trick allows us to generalize this to desiderata of the form:

To achieve this, we postulate a predictor that guesses the policy, producing the guess , and define the fuzzy belief using the function (we assume the guess is not influenced by the agent's actions so we don't need in the expected value). Using Nirvana trick, we effectively force the guess to be accurate.

In particular, this captures self-referential desiderata of the type "the policy cannot be improved by changing it in this particular way". These are of the form:

It also allows us to effectively restrict the policy space (e.g. impose computational resource constraints) by setting to for policies outside the space.

The fact that quasi-Bayesian RL is so general can also be regarded as a drawback: the more general a framework the less information it contains, the less useful constraints it imposes. But, my perspective is that QBRL is the correct starting point, after which we need to start proving results about which fuzzy hypotheses classes are learnable, and within what sample/computational complexity. So, although QBRL in itself doesn't impose much restrictions on what the agent should be, it provides the natural language in which desiderata should be formulated. In addition, we can already guess/postulate that an ideal rational agent should be a QBRL agent whose fuzzy prior is universal in some appropriate sense.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-13T17:36:40.891Z · LW(p) · GW(p)

Well, I think that maximin is the right thing to do because it leads to reasonable guarantees for quasi-Bayesian reinforcement learning agents. I think of incomplete models as properties that the environment might satisfy. It is necessary to speak of properties instead of complete models since the environment might be too complex to understand in full (for example because it contains Omega, but also for more prosaic reasons), but we can hope it at least has properties/patterns the agent can understand. A quasi-Bayesian agent has the guarantee that, whenever the environment satisfies one of the properties in its prior, the expected utility will converge at least to the maximin for this property. In other words, such an agent is able to exploit any true property of the environment it can understand. Maybe a more "philosophical" defense of maximin is possible, analogous to VNM / complete class theorems, but I don't know (I actually saw some papers in that vein but haven't read them in detail.)

If the agent has random bits that Omega doesn't see, and Omega is predicting the probabilities of the agent's actions, then I think we can still solve it with quasi-Bayesian agents but it requires considering more complicated models and I haven't worked out the details. Specifically, I think that we can define some function that depends on the agent's actions and Omega's predictions so far (a measure of Omega's apparent inaccuracy), s.t. if Omega is an accurate predictor, then, the supremum of over time is finite with probability 1. Then, we consider consider a family of models, where model number says that for all times. Since at least one of these models is true, the agent will learn it, and will converge to behaving appropriately.

EDIT 1: I think should be something like, how much money would a gambler following a particular strategy win, betting against Omega.

EDIT 2: Here is the solution. In the case of original Newcomb, consider a gambler that bets against Omega on the agent one-boxing. Every time the agent two-boxes, the gambler loses dollar. Every time the agent one-boxes, the gambler wins dollars, where is the probability Omega assigned to one-boxing. Now it's possible to see that one-boxing guarantees the "CC" payoff under the corresponding model (in the limit): If the agent one-boxes, the gambler keeps winning unless Omega converges to one-boxing rapidly enough. In the case of a general Newcomb-like problem, just replace "one-boxes" by "follows the FDT strategy".

comment by Linda Linsefors · 2019-11-13T14:09:50.217Z · LW(p) · GW(p)

I agree that you can assign what ever belief you want (e.g. what ever is useful for the agents decision making proses) for for what happens in the counterfactual when omega is wrong, in decision problems where Omega is assumed to be a perfect predictor. However if you want to generalise to cases where Omega is an imperfect predictor (as you do mention), then I think you will (in general) have to put in the correct reward for Omega being wrong, becasue this is something that might actually be observed.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-13T14:13:34.768Z · LW(p) · GW(p)

The method should work for imperfect predictors as well. In the simplest case, the agent can model the imperfect predictor as perfect predictor + random noise. So, it definitely knows the correct reward for Omega being wrong. It still believes in Nirvana if "idealized Omega" is wrong.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-04-10T17:04:36.009Z · LW(p) · GW(p)

Epistemic status: moderately confident, based on indirect evidence

I realized that it is very hard to impossible to publish an academic work that takes more than one conceptual inferential step away from the current paradigm. Especially when the inferential steps happen in different fields of knowledge.

You cannot publish a paper where you use computational learning theory to solve metaphysics, and then use the new metaphysics to solve the interpretation of quantum mechanics. A physics publication will not understand the first part, or even understand how it can be relevant. As a result, they will also fail to understand the second part. A computer science publication will not understand or be interested in the second part.

Publishing the two parts separately one after the other also won’t work. The first part might be accepted, but the reviewers of the second part won’t be familiar with it, and the same problems will resurface. The only way to win seems to be: publish the first part, wait until it becomes widely accepted, and only then publish the second part.

comment by Dagon · 2020-04-10T17:54:14.420Z · LW(p) · GW(p)

Hmm. I think I need more detail on your model of publishing and wide-acceptance and their relationship to truth. It seems likely that unless they're circularly dependent, you can publish the smaller-departure in parallel with exploring the further implications in different journals, and in research agendas rather than results publication.

comment by Pattern · 2020-04-12T23:01:12.204Z · LW(p) · GW(p)

So there's journals of X, Y, and Z, but not XYZ?

(In hindsight this sounds obvious, though the only obvious alternatives would be

  • it's hard, but the hardness is in figuring out which place can handle the combination/complexity
  • Publishing anything is hard (or there's a limit to the time/space allocated per month, and timing matters)
comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-18T13:22:25.051Z · LW(p) · GW(p)

Consider a Solomonoff inductor predicting the next bit in the sequence {0, 0, 0, 0, 0...} At most places, it will be very certain the next bit is 0. But, at some places it will be less certain: every time the index of the place is highly compressible. Gradually it will converge to being sure the entire sequence is all 0s. But, the convergence will be very slow: about as slow as the inverse Busy Beaver function!

This is not just a quirk of Solomonoff induction, but a general consequence of reasoning using Occam's razor (which is the only reasonable way to reason). Of course with bounded algorithms the convergence will be faster, something like the inverse bounded-busy-beaver, but still very slow. Any learning algorithm with inductive bias towards simplicity will have generalization failures when coming across the faultlines that carve reality at the joints, at every new level of the domain hierarchy.

This has an important consequence for alignment: in order to stand a chance, any alignment protocol must be fully online, meaning that whatever data sources it uses, those data sources must always stay in the loop, so that the algorithm can query the data source whenever it encounters a faultline. Theoretically, the data source can be disconnected from the loop at the point when it's fully "uploaded": the algorithm unambiguously converged towards a detailed accurate model of the data source. But in practice the convergence there will be very slow, and it's very hard to know that it already occurred: maybe the model seems good for now but will fail at the next faultline. Moreover, convergence might literally never occur if the machine just doesn't have the computational resources to contain such an upload (which doesn't mean it doesn't have the computational resources to be transformative!)[1]

This is also a reason for pessimism regarding AI outcomes. AI scientists working through trial and error will see the generalization failures becoming more and more rare, with longer and longer stretches of stable function in between. This creates the appearance of increasing robustness. But, in reality robustness increases very slowly. We might reach a stable stretch between "subhuman" and "far superhuman" and the next faultline will be the end.

  1. In the Solomonoff analogy, we can imagine the real data source as a short but prohibitively expensive program, and the learned model of the data source as an affordable but infinitely long program: as time progresses, more and more bits of this program will be learned, but there will always be bits that are still unknown. Of course, any prohibitively expensive program can be made affordable by running it much slower than real-time, which is something that Turing RL [LW(p) · GW(p)] can exploit, but at some point this becomes impractical. ↩︎

comment by crabman · 2020-08-19T05:49:31.073Z · LW(p) · GW(p)

An alignment-unrelated question: Can we, humans, increase the probability that something weird happens in our spacetime region (e.g., the usual laws of physics stop working) by making it possible to compress our spacetime location? E.g., by building a structure that is very regular (meaning that its description can be very short) and has never been built before in our space region, something like make a huge perfectly aligned rectangular grid of hydrogen atoms, or something like that.

It's like a magical ritual for changing the laws of physics. This gives a new meaning to summoning circles, pentagrams, etc.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-19T13:31:38.881Z · LW(p) · GW(p)

We can rephrase your question as follows: "Can we increase the probability of finding an error in the known laws of physics by performing an experiment with a simple property that never happened before, either naturally or artificially"? And the answer is: yes! This is actually what experimental physicists do all the time: perform experiments that try to probe novel circumstances where it is plausible (Occam-razor-wise) that new physics will be discovered.

As to magical rituals, sufficiently advanced technology is indistinguishable from magic :)

comment by MikkW (mikkel-wilson) · 2020-08-20T03:13:21.731Z · LW(p) · GW(p)

I have a sense that similar principles are at play with Spaced Repetition, and that pointing out that connection may be relevant to effectively handling this issue

comment by ofer · 2020-08-19T18:59:44.072Z · LW(p) · GW(p)

convergence might literally never occur if the machine just doesn’t have the computational resources to contain such an upload

I think that in embedded settings (with a bounded version of Solomonoff induction) convergence may never occur, even in the limit as the amount of compute that is used for executing the agent goes to infinity. Suppose the observation history contains sensory data that reveals the probability distribution that the agent had, in the last time step, for the next number it's going to see in the target sequence. Now consider the program that says: "if the last number was predicted by the agent to be 0 with probability larger than then the next number is 1; otherwise it is 0." Since it takes much less than bits to write that program, the agent will never predict two times in a row that the next number is 0 with probability larger than (after observing only 0s so far).

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-12-21T16:04:01.467Z · LW(p) · GW(p)

One subject I like to harp on is reinforcement learning with traps (actions that cause irreversible long term damage). Traps are important for two reasons. One is that the presence of traps is in the heart of the AI risk concept: attacks on the user, corruption of the input/reward channels, and harmful self-modification can all be conceptualized as traps. Another is that without understanding traps we can't understand long-term planning, which is a key ingredient of goal-directed intelligence.

In general, a prior that contains traps will be unlearnable, meaning that no algorithm has Bayesian regret going to zero in the limit. The only obvious natural requirement for RL agents in this case is approximating Bayes-optimality. However, Bayes-optimality is not even "weakly feasible": it is NP-hard w.r.t. using the number of states and number of hypotheses as security parameters. IMO, the central question is: what kind of natural tractable approximations are there?

Although a generic prior with traps is unlearnable, some priors with traps are learnable. Indeed, it can happen that it's possible to study the environment is a predictably safe way that is guaranteed to produce enough information about the irreversible transitions. Intuitively, as humans we do often use this kind of strategy. But, it is NP-hard to even check whether a given prior is learnable. Therefore, it seems natural to look for particular types of learnable priors that are efficiently decidable.

In particular, consider the following setting, that I call "expanding safety envelope" (XSE). Assume that each hypothesis in the prior is "decorated" by a set of state-action pairs s.t. (i) any is safe, i.e. the leading term of in the expansion is maximal (ii) for each , there is s.t. is Blackwell-optimal for (as a special case we can let contain all safe actions). Imagine an agent that takes random actions among those a priori known to be in . If there is no such action, it explodes. Then, it is weakly feasible to check (i) whether the agent will explode (ii) for each hypothesis, to which sets of states it can converge. Now, let the agent update on the transition kernel of the set of actions it converged to. This may lead to new actions becoming certainly known to be in . We can then let the agent continue exploring using this new set. Iterating this procedure, the agent either discovers enough safe actions to find an optimal policy, or not. Importantly, deciding this is weakly feasible. This is because, for each hypothesis (i) on the first iteration the possible asymptotic state sets are disjoint (ii) on subsequent iterations we might as well assume they are disjoint, since it's possible to see that if you reach a particular state of an asymptotic set state, then you can add the entire set state (this modification will not create new final outcomes and will only eliminate final outcomes that are better than those remaining). Therefore the number of asymptotic state sets you have to store on each iteration is bounded by the total number of states.

The next questions are (i) what kind of regret bounds we can prove for decorated priors that are XSE-learnable? (ii) given an arbitrary decorated prior, is it possible to find the maximal-probability-mass set of hypotheses, which is XSE-learnable? I speculate that the second question might turn out to be related to the unique games conjecture. By analogy with other optimization problems that are feasible only when maximal score can be achieved, maybe the UGC implies that we cannot find the maximal set but we can find a set that is approximately maximal, with an optimal approximation ratio (using a sum-of-squares algorithm). Also, it might make sense to formulate stronger desiderata which reflect that, if the agent assumes a particular subset of the prior but discovers that it was wrong, it will still do its best in the following. That is, in this case the agent might fall into a trap but at least it will try to avoid further traps.

This has implications even for learning without traps. Indeed, most known theoretical regret bounds involve a parameter that has to do with how costly mistakes is it possible to make. This parameter can manifest as the MDP diameter, the bias span or the mixing time. Such regret bounds seem unsatisfactory since the worst-case mistake determines the entire guarantee. We can take the perspective that such costly but reversible mistakes are "quasi-traps": not actual traps, but trap-like on short timescales. This suggests that applying an approach like XSE to quasi-traps should lead to qualitatively stronger regret bounds. Such regret bounds would imply learning faster on less data, and in episodic learning they would imply learning inside each episode, something that is notoriously absent in modern episodic RL systems like AlphaStar.

Moreover, we can also use this to do away with ergodicity assumptions. Ergodicity assumptions require the agent to "not wander too far" in state space, in the simplest case because the entire state space is small. But, instead of "wandering far" from a fixed place in state space, we can constrain "wandering far" w.r.t. to the optimal trajectory. Combining this with XSE, this should lead to guarantees that depend on the prevalence of irreversible and quasi-irreversible departures from this trajectory.

In multi-armed bandits and RL theory, there is a principle known as "optimism in the face of uncertainty". This principle says, you should always make optimistic assumptions: if you are wrong, you will find out (because you will get less reward than you expected). It explicitly underlies UCB algorithms and is implicit in other algorithms, like Thomson sampling. But, this fails miserably in the presence of traps. I think that approaches like XSE point at a more nuanced principle: "optimism in the face of cheap-to-resolve uncertainty, pessimism in the face of expensive-to-resolve uncertainty". Following this principle doesn’t lead to actual Bayes-optimality, but perhaps it is in some sense a good enough approximation.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-28T16:41:44.233Z · LW(p) · GW(p)

Master post for ideas about infra-Bayesianism [? · GW].

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-09-28T17:29:06.071Z · LW(p) · GW(p)

There is a formal analogy between infra-Bayesian decision theory (IBDT) and modal updateless decision theory [AF · GW] (MUDT).

Consider a one-shot decision theory setting. There is a set of unobservable states , a set of actions and a reward function . An IBDT agent has some belief [1], and it chooses the action .

We can construct an equivalent scenario, by augmenting this one with a perfect predictor of the agent (Omega). To do so, define , where the semantics of is "the unobservable state is and Omega predicts the agent will take action ". We then define by and by ( is what we call the pullback of to , i.e we have utter Knightian uncertainty about Omega). This is essentially the usual Nirvana construction.

The new setup produces the same optimal action as before. However, we can now give an alternative description of the decision rule.

For any , define by . That is, is an infra-Bayesian representation of the belief "Omega will make prediction ". For any , define by . can be interpreted as the belief "assuming Omega is accurate, the expected reward will be at least ".

We will also need to use the order on defined by: when . The reversal is needed to make the analogy to logic intuitive. Indeed, can be interpreted as " implies "[2], the meet operator can be interpreted as logical conjunction and the join operator can be interpreted as logical disjunction.


(Actually I only checked it when we restrict to crisp infradistributions, in which case is intersection of sets and is set containment, but it's probably true in general.)

Now, can be interpreted as "the conjunction of the belief and implies ". Roughly speaking, "according to , if the predicted action is then the expected reward is at least ". So, our decision rule says: choose the action that maximizes the value for which this logical implication holds (but "holds" is better thought of as "is provable", since we're talking about the agent's belief). Which is exactly the decision rule of MUDT!

  1. Apologies for the potential confusion between as "space of infradistrubutions" and the of modal logic (not used in this post). ↩︎

  2. Technically it's better to think of it as " is true in the context of ", since it's not another infradistribution so it's not a genuine implication operator. ↩︎

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-10-02T16:54:29.827Z · LW(p) · GW(p)

In the anthropic trilemma [LW · GW], Yudkowsky writes about the thorny problem of understanding subjective probability in a setting where copying and modifying minds is possible. Here, I will argue that infra-Bayesianism (IB) leads to the solution.

Consider a population of robots, each of which in a regular RL agent. The environment produces the observations of the robots, but can also make copies or delete portions of their memories. If we consider a random robot sampled from the population, the history they observed will be biased compared to the "physical" baseline. Indeed, suppose that a particular observation has the property that every time a robot makes it, 10 copies of them are created in the next moment. Then, a random robot will have much more often in their history than the physical frequency with which is encountered, due to the resulting "selection bias". We call this setting "anthropic RL" (ARL).

The original motivation for IB was non-realizability. But, in ARL, Bayesianism runs into issues even when the environment is realizable from the "physical" perspective. For example, we can consider an "anthropic MDP" (AMDP). An AMDP has finite sets of actions () and states (), and a transition kernel . The output is a string of states instead of a single state, because many copies of the agent might be instantiated on the next round, each with their own state. In general, there will be no single Bayesian hypothesis that captures the distribution over histories that the average robot sees at any given moment of time (at any given moment of time we sample a robot out of the population and look at their history). This is because the distributions at different moments of time are mutually inconsistent.

The consistency that is violated is exactly the causality property of environments. Luckily, we know how to deal with acausality: using the IB causal-acausal correspondence! The result can be described as follows: Murphy chooses a time moment and guesses the robot policy until time . Then, a simulation of the dynamics of is performed until time , and a single history is sampled from the resulting population. Finally, the observations of the chosen history unfold in reality. If the agent chooses an action different from what is prescribed, Nirvana results. Nirvana also happens after time (we assume Nirvana reward rather than ).

This IB hypothesis is consistent with what the average robot sees at any given moment of time. Therefore, the average robot will learn this hypothesis (assuming learnability). This means that for , the population of robots at time has expected average utility with a lower bound close to the optimum for this hypothesis. I think that for an AMDP this should equal the optimum expected average utility you can possibly get, but it would be interesting to verify.

Curiously, the same conclusions should hold if we do a weighted average over the population, with any fixed method of weighting. Therefore, the posterior of the average robot behaves adaptively depending on which sense of "average" you use. So, your epistemology doesn't have to fix a particular method of counting minds. Instead different counting methods are just different "frames of reference" through which to look, and you can be simultaneously rational in all of them.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-30T19:55:38.445Z · LW(p) · GW(p)

One of the central challenges in Dialogic Reinforcement Learning [AF(p) · GW(p)] is dealing with fickle users, i.e. the user changing eir mind in illegible ways that cannot necessarily be modeled as, say, Bayesian updating. To take this into account, we cannot use the naive notion of subjective regret bound, since the user doesn't have a well-defined prior. I propose to solve this by extending the notion of dynamically inconsistent preferences [AF(p) · GW(p)] to dynamically inconsistent beliefs. We think of the system as a game, where every action-observation history corresponds to its own player. The action space of each player is just . An outcome of such a game can be also thought of as a policy for the AI. The payoff of a player is expected utility (for this player's reward function) w.r.t. the probability measure resulting from plus the current belief state of the user conditional on , ( is the set of possible "realities"). We then define regret as the sum of Bellman errors w.r.t. equilibrium value of the players that actually manifested (so that in equilibrium it is zero). Bayesian regret requires taking expected value w.r.t some "ur-prior" that the AI starts with. Note that:

  • For a user that updates its beliefs on the AI's observations according the Bayes' theorem, the regret per reality is the same as subjective regret. Bayesian regret is also the same if the ur-prior assumes the user's beliefs are calibrated (which in the more general case is not a necessary assumption). The same applies to a user that doesn't updates eir beliefs at all.

  • The user beliefs are part of the ontology . Therefore, the system takes into accounts the user's beliefs about the evolution of the user's beliefs. So, the equilibrium policy is incentivized to empower its future self to the extent that the user believes that eir own beliefs will become more accurate over time (given fixed reward function, see below).

  • contains a distinct reward function for each player. And, the user may have uncertainty even over eir own current reward function. Therefore, the system distinguishes two types of value modifications: "legitimate" modifications that consist of improving one's beliefs about the reward function and "illegitimate" modification that consist of the reward function actually changing. The equilibrium policy is incentivized to encourage the first type and avoid the second type.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-09T15:03:29.702Z · LW(p) · GW(p)

There is a deficiency in this "dynamically subjective" regret bound (also can be called "realizable misalignment" bound) as a candidate formalization of alignment. It is not robust to scaling down [AF · GW]. If the AI's prior allows it to accurately model the user's beliefs (realizability assumption), then the criterion seems correct. But, imagine that the user's beliefs are too complex and an accurate model is not possible. Then the realizability assumption is violated and the regret bound guarantees nothing. More precisely, the AI may use incomplete models [AF · GW] to capture some properties of the user's beliefs and exploit them, but this might be not good enough. Therefore, such an AI might fall into a dangerous zone when it is powerful enough to cause catastrophic damage but not powerful enough to know it shouldn't do it.

To fix this problem, we need to introduce another criterion which has to hold simultaneously with the misalignment bound. We need that for any reality that satisfies the basic assumptions built into the prior (such as, the baseline policy is fairly safe, most questions are fairly safe, human beliefs don't change too fast etc), the agent will not fail catastrophically. (It would be way too much to ask it would converge to optimality, it would violate no-free-lunch.) In order to formalize "not fail catastrophically" I propose the following definition.

Let's start with the case when the user's preferences and beliefs are dynamically consistent. Consider some AI-observable event that might happen in the world. Consider a candidate learning algorithm and two auxiliary policies. The policy follows the baseline policy until happens, at which time it switches to the subjectively optimal policy. The policy follows the candidate learning algorithm until happens, at which time it also switches to the subjectively optimal policy. Then, the "-dangerousness" of is defined to be the expected utility of minus the expected utility of . Thus, when -incorrigibility is zero or negative, does no worse than .

Why do we need ? Because without the criterion would allow policies that don't damage the present but permanently destroy opportunities that could be used by a future better AI.

In the dynamically consistent case, incorrigibility can be represented as an expected sum over time-before- of Bellman errors w.r.t the value function of . This allows us generalizing it to the dynamically inconsistent case, by writing a similar expression except that each Bellman error term uses the transient preferences and beliefs of the user at the given moment.

Is it truly possible to have a reasonable bound on -dangerousness for all , and is it possible to do so while maintaining a reasonable realizable misalignment bound? It seems possible, for the following reason. The user's beliefs can be represented as a mapping from questions to answers(fn1). If you sample questions from any fixed distribution, then by verifying that you can predict the answers, you gain valid information about the belief state without any prior about the belief state (it is a "frequentist" guarantee). Therefore, the AI can constrain itself to taking only those actions which are known to be safe based on this "robust" information. Since there is no guarantee that the AI will find a model that predicts answers, in the unrealizable case this might leave it without an effective strategy, but even without any information the AI can stay safe by following the baseline.

This notion of dangerousness seems strongly related to corrigibility. To demonstrate, imagine an attempt by the user to shut down the AI. Suppose that the AI has 3 strategies with which to respond: (i) comply with the shut down (ii) resist defensively, i.e. prevent shutdown but without irreversible damaging anything (iii) resist offensively, e.g. by doing something irreversible to the user that will cause em to stop trying to shut down the AI. The baseline policy is complying. Then, assuming that the user's stated beliefs endorse the shutdown, an AI with low dangerousness should at most resist defensively for a short period and then comply. That's because resisting offensively would generate high dangerousness by permanent loss of value, whereas resisting defensively for a long time would generate high dangerousness by losing reward over that period. At the least, this is much more corrigible than CIRL which guarantees nothing in the unrealizable case, and even in the realizable case no general guarantees were obtained (and arguably cannot be obtained since the AI might not have enough information).

This notion of dangerousness opens the way towards designing AI systems that are provably safe while at the same time employing heuristic algorithms without theoretical understanding. Indeed, as long as the AI has sufficiently low dangerousness, it will almost certainly not cause catastrophic damage. A misalignment bound is only needed to prove the AI will also be highly capable at pursuing the user's goals. The way such a heuristic AI may work, is by producing formal certificates for each action it takes. Then, we need not trust the mechanism suggesting the actions nor the mechanism producing the certificates, as long as we trust the verification of those certificates (which doesn't require AI). The untrustworthy part might still be dangerous if it can spawn non-Cartesian daemons [AF · GW] But, that is preventable using TRL [AF(p) · GW(p)], assuming that the "core" agent has low dangerousness and is too weak to spawn superhuman daemons without the "envelope".

(fn1) In truth, this assumption that the user's answers come from a mapping that changes only slowly is probably unrealistic, because the user need not have coherent beliefs even over short timescales. For example, there might be many pairs of fairly ordinary (non-manipulative) questions s.t. asking them in different order will produce different answers. However, to the extent that the user's beliefs are incoherent, and therefore admit multiple equally plausible interpretations, learning any interpretation should be good enough. Therefore, although the model needs to be made more general, the learning problem should not become substantially more difficult.

comment by TurnTrout · 2020-01-19T02:29:19.720Z · LW(p) · GW(p)

This notion of dangerousness seems strongly related to corrigibility. To demonstrate, imagine an attempt by the user to shut down the AI. Suppose that the AI has 3 strategies with which to respond: (i) comply with the shut down (ii) resist defensively, i.e. prevent shutdown but without irreversible damaging anything (iii) resist offensively, e.g. by doing something irreversible to the user that will cause em to stop trying to shut down the AI. The baseline policy is complying. Then, assuming that the user's stated beliefs endorse the shutdown, an AI with low dangerousness should at most resist defensively for a short period and then comply. That's because resisting offensively would generate high dangerousness by permanent loss of value, whereas resisting defensively for a long time would generate high dangerousness by losing reward over that period...

This notion of dangerousness opens the way towards designing AI systems that are provably safe while at the same time employing heuristic algorithms without theoretical understanding. Indeed, as long as the AI has sufficiently low dangerousness, it will almost certainly not cause catastrophic damage.

This seems quite close (or even identical) to attainable utility preservation; if I understand correctly, this echoes arguments I've made [LW(p) · GW(p)] for why AUP has a good shot of avoiding catastrophes and thereby getting you something which feels similar to corrigibility.

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-01-19T15:29:37.226Z · LW(p) · GW(p)

There is some similarity, but there are also major differences. They don't even have the same type signature. The dangerousness bound is a desideratum that any given algorithm can either satisfy or not. On the other hand, AUP is a specific heuristic how to tweak Q-learning. I guess you can consider some kind of regret bound w.r.t. the AUP reward function, but they will still be very different conditions.

The reason I pointed out the relation to corrigibility is not because I think that's the main justification for the dangerousness bound. The motivation for the dangerousness bound is quite straightforward and self-contained: it is a formalization of the condition that "if you run this AI, this won't make things worse than not running the AI", no more and no less. Rather, I pointed the relation out to help readers compare it with other ways of thinking they might be familiar with.

From my perspective, the main question is whether satisfying this desideratum is feasible. I gave some arguments why it might be, but there are also opposite arguments. Specifically, if you believe that debate is a necessary component of Dialogic RL then it seems like the dangerousness bound is infeasible. The AI can become certain that the user would respond in a particular way to a query, but it cannot become (worst-case) certain that the user would not change eir response when faced with some rebuttal. You can't (empirically and in the worst-case) prove a negative.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-02T13:41:19.230Z · LW(p) · GW(p)

Dialogic RL assumes that the user has beliefs about the AI's ontology. This includes the environment(fn1) from the AI's perspective. In other words, the user needs to have beliefs about the AI's counterfactuals (the things that would happen if the AI chooses different possible actions). But, what are the semantics of the AI's counterfactuals from the user's perspective? This is more or less the same question that was studied by the MIRI-sphere for a while, starting from Newcomb's paradox, TDT et cetera. Luckily, I now have an answer [AF(p) · GW(p)] based on the incomplete models formalism. This answer can be applied in this case also, quite naturally.

Specifically, we assume that there is a sense, meaningful to the user, in which ey select the AI policy (program the AI). Therefore, from the user's perspective, the AI policy is a user action. Again from the user's perspective, the AI's actions and observations are all part of the outcome. The user's beliefs about the user's counterfactuals can therefore be expressed as (fn2), where is the space of AI policies(fn3). We assume that for every , is consistent with the natural sense. Such a belief can be transformed into an incomplete model from the AI's perspective, using the same technique we used to solve Newcomb-like decision problems, with playing the role of Omega. For a deterministic AI, this model looks like (i) at first, "Murphy" makes a guess that the AI's policy is (ii) The environment behaves according to the conditional measures of (iii) If the AI's policy ever deviates from , the AI immediately enters an eternal "Nirvana" state with maximal reward. For a stochastic AI, we need to apply the technique with statistical tests and multiple models alluded to in the link. This can also be generalized to the setting where the user's beliefs are already an incomplete model, by adding another step where Murphy chooses out of some set.

What we constructed is a method of translating counterfactuals from the user's perspective to the AI's perspective. In particular, the AI will inherit the user's level of "updatelessness" (in the sense that, if the user's counterfactuals are defined w.r.t. a particular effective precommitment point, the AI will use the same point). This translation may be implemented either (i) by the user, by explaining these semantics to em or (ii) by the AI, in which case the formal language should refer to the user's counterfactuals rather than the AI's counterfactuals.

(fn1) Up to an equivalence relation, that's a mapping .

(fn2) For infinite AI liftetime. We can trivially generalize this to allow for finite AI lifetime as well.

(fn3) Up to an equivalence relation, they are mappings . We may add computability/complexity constraints and represent them as programs.

comment by Gurkenglas · 2019-11-02T14:02:11.345Z · LW(p) · GW(p)

Nirvana and the chicken rule both smell distasteful like proofs by contradiction, as though most everything worth doing can be done without them, and more canonically to boot.

(Conjecture: This can be proven, but only by contradiction.)

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-02T14:52:53.186Z · LW(p) · GW(p)

Maybe? I am not sure that I like Nirvana, but it doesn't seem that bad. If someone thinks of a solution without it, I would be interested.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-31T15:16:55.351Z · LW(p) · GW(p)

Another notable feature of this approach is its resistance to "attacks from the future", as opposed to approaches based on forecasting. In the latter, the AI has to predict some future observation, for example what the user will write after working on some problem for a long time. In particular, this is how the distillation step in IDA is normally assumed to work, AFAIU. Such a forecaster might sample a future in which a UFAI has been instantiated and this UFAI will exploit this to infiltrate the present. This might result in a self-fulfilling prophecy, but even if the forecasting is counterfactual (and thus immune to self-fulfilling prophecies)it can be attacked by a UFAI that came to be for unrelated reasons. We can ameliorate this by making the forecasting recursive (i.e. apply multiple distillation & amplification steps) or use some other technique to compress a lot of "thinking time" into a small interval of physical time. However, this is still vulnerable to UFAIs that might arise already at present with a small probability rate (these are likely to exist since our putative FAI is deployed at a time when technology progressed enough to make competing AGI projects a real possibility).

Now, compare this to Dialogical RL, as defined via the framework of dynamically inconsistent beliefs. Dialogical RL might also employ forecasting to sample the future, presumably more accurate, beliefs of the user. However, if the user is aware of the possibility of a future attack, this possibility is reflected in eir beliefs, and the AI will automatically take it into account and deflect it as much as possible.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-31T00:23:43.683Z · LW(p) · GW(p)

This approach also obviates the need for an explicit commitment mechanism. Instead, the AI uses the current user's beliefs about the quality of future user beliefs to decide whether it should wait for user's beliefs to improve or commit to an irreversible coarse of action. Sometimes it can also predict the future user beliefs instead of waiting (predict according to current user beliefs updated by the AI's observations).

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-31T00:22:14.948Z · LW(p) · GW(p)

(moved to alignment forum)

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-21T15:36:20.122Z · LW(p) · GW(p)

In my previous shortform [AF(p) · GW(p)], I used the phrase "attack vector", borrowed from classical computer security. What does it mean to speak of an "attack vector" in the context of AI alignment? I use 3 different interpretations, which are mostly 3 different ways of looking at the same thing.

In the first interpretation, an attack vector is a source of perverse incentives. For example, if a learning protocol allows the AI to ask the user questions, a carefully designed question can artificially produce an answer we would consider invalid, for example by manipulating the user or even by hacking the software or hardware of the system in some clever way. If the algorithm treats every answer as valid, this creates a perverse incentive: the AI knows that by phrasing the question in a particular way, a certain answer will result, so it will artificially obtain the answers that are preferable (for example answers that produce an easier to optimize utility function). In this interpretation the "attacker" is the AI itself. In order to defend against the vector, we might change the AI's prior so that the AI knows some of the answers are invalid. If the AI has some method of distinguishing valid from invalid answers, that would eliminate the perverse incentive.

In the second interpretation, an attack vector is a vulnerability that can be exploited by malicious hypotheses in the AI's prior. Such a hypothesis is an agent with its own goals (for example, it might arise as a simulation hypothesis). This agent intentionally drives the system to ask manipulative questions to further these goals. In order to defend, we might design the top level learning algorithm so that it only takes action that are safe with sufficiently high confidence (like in Delegative RL). If the prior contains a correct hypothesis along with the malicious hypothesis, the attack is deflected (since the correct hypothesis deems the action unsafe). Such a confidence threshold can usually be viewed as a computationally efficient implementation of the prior shaping described in the previous paragraph.

In the third interpretation, an attack vector is something that impedes you from proving a regret bound under sufficiently realistic assumptions. If your system has an undefended question interface, then proving a regret bound requires assuming that asking a question cannot create irreversible damage. In order to drop this assumption, a defense along the lines of the previous paragraphs has to be employed.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-18T12:26:33.081Z · LW(p) · GW(p)

The sketch of a proposed solution to the hard problem of consciousness: An entity is conscious if and only if (i) it is an intelligent agent (i.e. a sufficiently general reinforcement learning system) and (ii) its values depend on the presence and/or state of other conscious entities. Yes, this definition is self-referential, but hopefully some fixed point theorem applies. There may be multiple fixed points, corresponding to "mutually alien types of consciousness".

Why is this the correct definition? Because it describes precisely the type of agent who would care about the hard problem of consciousness.

comment by cousin_it · 2019-11-13T12:07:24.159Z · LW(p) · GW(p)

I'm not sure your definition has much to do with consciousness, as it would also be satisfied by an AI that runs on an Intel processor and whose utility function says all AIs should run on Intel processors.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-13T13:30:32.562Z · LW(p) · GW(p)

Its utility function would have to say that all conscious AIs should run on Intel processors. There is self-reference there.

But, I only have rather low confidence this idea is correct (what being correct means here) or important.

comment by G Gordon Worley III (gworley) · 2019-10-18T18:13:34.448Z · LW(p) · GW(p)

This seems to me to address the meta problem of consciousness rather than the hard problem of consciousness itself, since you seem to be more offering an etiology for the existence of agents that would care about the hard problem of consciousness rather than an etiology of qualia.

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-19T12:03:40.698Z · LW(p) · GW(p)

Yes, but I also claim that the agents that would care about the hard problem of consciousness are exactly the agents that are themselves conscious.

comment by mr-hire · 2019-10-18T14:23:11.453Z · LW(p) · GW(p)

I'm trying to figure out what precisely #2 means. How do you define "values"? IE, if I'm a deep learning algorithm in a tournament with other deep learning algorithms, certainly my instrumental values depend on the state of other deep learning algorithms. Is that sufficient in your definition for consciousness?

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-10-18T14:40:47.455Z · LW(p) · GW(p)

No, I am talking about terminal values. Something like an instrumental reward function [AF · GW] specified via an ontology that involves consciousness. Also, I am not sure deep learning in its present form qualifies as sufficiently "general" for (i).

comment by Gurkenglas · 2019-10-21T15:02:35.484Z · LW(p) · GW(p)

Your definition says that people's models of other people can be conscious, doesn't it?

comment by Vanessa Kosoy (vanessa-kosoy) · 2020-08-31T19:40:25.308Z · LW(p) · GW(p)

A summary of my current breakdown of the problem of traps into subproblems and possible paths to solutions. Those subproblems are different but different but related. Therefore, it is desirable to not only solve each separately, but also to have an elegant synthesis of the solutions.

Problem 1: In the presence of traps, Bayes-optimality becomes NP-hard even on the weakly feasible level (i.e. using the number of states, actions and hypotheses as security parameters).

Currently I only have speculations about the solution. But, I have a few desiderata for it:

Desideratum 1a: The algorithm should guarantee some lower bound on expected utility, compared to what the Bayes-optimal policy gets. We should also have an upper bound for all polynomial time algorithms. The two bounds should not be too far apart.

Desideratum 1b: When it so happens we have no traps, the algorithm should produce asymptotic Bayes optimality with a regret bound close enough to optimal. When there are only "small" traps, the penalty should be proportional.

Problem 2:: In the presence of traps, there is no "frequentist" guarantee (regret bound). We can divide it into subproblems according to different motivations for having such a guarantee in the first place.

Problem 2a: We want such a guarantee as a certificate of safety.

Solution: Require a subjective [AF(p) · GW(p)] regret [AF(p) · GW(p)] bound instead.

Problem 2b: The guarantee is motivated by an "evolutionary" perspective on intelligence: intelligent agents are agents that are successful in the real world, not just in average over all possible worlds.

Solution: Bootstrapping from a safe baseline policy [AF(p) · GW(p)]. For an individual human, the baseline comes from knowledge learned from other people. For human civilization, some of the baseline comes from inborn instincts. For human civilization and evolution both, the baseline comes from locality and thermodynamics: doing random things is unlikely to cause global irreversible damage. For an aligned AI, the baseline comes from imitation learning and quantilization.

Problem 2c: The guarantee is needed to have a notion of "sample complexity", which is such an important concept that it's hard to imagine deconfusion without it. This notion cannot come just from Desideratum 1a since sample complexity should remain non-trivial even given unbounded computational resources.

Solution: A prior consists of a space of hypotheses and a probability measure over this space. We also have a mapping where is the space of environments, which provides semantics to the hypotheses. Bayes-optimizing means Bayes-optimizing the environment . Learnability of means that the Bayesian regret must converge to as goes to . Here is the (normalized to ) value (maximal expected utility) of environment at time discount . Notice that the second term depends only on but the first term depends on and . Therefore, we can ask about the regrets for different decompositions of the same into hypotheses. For some , and s.t. , we can have learnability even when we don't have it for the original decomposition. I think that typically there will be many such decompositions. They live in the convex set surrounding in which the value function becomes affine in the limit. We can say that not all information is learnable, but represents some learnable information. We can then study the regret bound (and thus) sample complexity for a particular or for all possible .

comment by Vanessa Kosoy (vanessa-kosoy) · 2019-11-08T18:14:31.729Z · LW(p) · GW(p)

It seems useful to consider agents that reason in terms of an unobservable ontology, and may have uncertainty over what this ontology is. In particular, in Dialogic RL [AF(p) · GW(p)], the user's preferences are probably defined w.r.t. an ontology that is unobservable by the AI (and probably unobservable by the user too) which the AI has to learn (and the user is probably uncertain about emself). However, onotlogies are more naturally thought of as objects in a category than as elements in a set. The formalization of an "ontology" should probably be a POMDP or a suitable Bayesian network. A POMDP involves an arbitrary set of states, so it's not an element in a set, and the class of POMDPs can be naturally made into a category. Therefore, there is need for defining the notion of a probability measure over a category. Of course we can avoid this by enumerating the states, considering the set of all possible POMDPs w.r.t. this enumeration and then requiring the probability measure to be invariant w.r.t. state relabeling. However, the category theoretic point of view seems more natural, so it might be worth fleshing out.

Ordinary probably measures are defined on measurable spaces. So, first we need to define the analogue of "measurable structure" (-algebra) for categories. Fix a category . Denote the category of measurable spaces. A measurable structure on is then specified by providing a Grothendick fibration and an equivalence . Here, stands for the essential fiber of over the one point space . The intended interpretation of is, the category of families of objects in indexed by measurable spaces. The functor is supposed to extract the base (index space) of the family. We impose the following conditions on and :

Given , and , we denote the corresponding base change by ( and is canonically isomorphic to ).

  • Consider and . Consider also a point . We can think of as a morphism . This allows us considering the base changes and (the "fibers" of at and at respectively) where . Applying the universal property of to and , we get morphisms . We now require that, if for any , then (morphisms between families that are pointwise equal are just equal).

  • Consider and . Suppose that (i) is an isomorphism and (ii) for any , is an isomorphism. Then, is an isomorphism (families with a common base that are pointwise isomorphic are just isomorphic).

I'm not entirely sure how sufficient or necessary these conditions are for proving useful results, but they seem to me natural at first glance. Note that this definition can be regarded as motivated by the Yoneda lemma: a measurable space is defined by the measurable mappings to from other measurable spaces, so a "measurable category" should be defined by the measurable "mappings" to it from measurable spaces, and is precisely the category of such measurable "mappings". Compare this with definition of geometric stacks(fn1).

Next, we define probability measures. Specifically, for any "measurable category" (a category equipped with structure as above), we construct the category of "probability measures on ". First, we define the auxiliary category . An object in is a pair where is an object in and is a probability measure on . We interpret this as sampling from and then taking (using , the latter can be considered to be an object in ). We define the morphisms from to as those morphisms for which (the notation stands for pushforward). Given , we call it a "quasi-isomorphism" when, for any , is an isomorphism. Claim: quasi-isomorphisms admit a calculus of right fractions(fn2). We now define as the localization of by quasi-isomorphisms.

(fn1) Maybe the analogy with stacks should be made more formal? Not sure, stacks are motivated by topology and measurable spaces are not topological...

(fn2) This should clearly be right, and this is right for natural examples, but I haven't written down the proof. If it turns out to be false it would mean that my conditions on are too weak.