Bayesian RPG system?

There are already RPG systems with non-linear probability distributions. GURPS has you throw 3d6, which is a rough approximation of a normal distribution. A +1 in 3d6 gets you to 63 % from 50 % and to 95 % from 91 %. The Fudge RPG system uses nonstandard dice which also have a distribution like this. It's not the decibel system, but it has the behavior you described and is usable without numeric tables or calculators.

Explicitly using probability decibels in game rules might be an interesting way to teach people to work with them though.

This is one of those sleep-deprived middle-of-the-night ideas which I'm reasonably likely to regret posting in the morning once I really wake up - but which, at least at the moment, thinking on my more-corrupted-than-standard hardware, seems like a cool idea.

Ah, self-handicapping in action...

Awesome idea, yes, but.... This doesn't have anything to do with Bayes.

The simplest way to use this as an RPG system seems to me to be coding it - this idea may be more available to me because I've recently been learning coffeescript by writing a DnD Pathfinder... engine, I suppose you'd call it. Do you mind if I learn myself a Bayesian implementation by trying out an implementation of your idea? Promise to share if I do.

(I have visions of a web client that handles character creation, feat interaction, spellbooks, permanency of statistics, and combat interaction, with a v2 of persistent campaign environments allowing players to perform limited actions like crafting without DM presence required and allowing people to pursue personal goals outside of session, all with the goal of inverting the standard D&D quote, "Dungeons and Dragons is 20 minutes of fun packed into 4 hours". This Bayesian RPG idea looks like it could work much the same way, or become the new project if this project becomes uninteresting to me.)

Incidentally, I compiled a list of design and development books for the roguelike game development wiki a few weeks ago, and wanted to find something about designing the stat and resolution rule systems in tabletop RPGs from a game design standpoint. Found nothing at all in books, and no online resource that seemed to go much beyond "these are the house rules I like based on this established system I like", as opposed to actually getting into the theory of why have stat systems to begin with, how the math works for the different variants and what the world simulation, human usability and game design implications of different choices of system are.

Now that you've woken up, why not try showing the math? E.g., why is a change from 50% to 66% "3 decibels" ? What would happen if you added 3 decibels to a previously "impossible" task (5%? 1%? 0.1%?)

Would this offer any benefit in terms of either fun or realism beyond the fudge dice, 3d6, etc. from other people's comments? What benefit? If the benefit is educational, what exactly would people learn?

One simple way of keeping that playable:

Each skill is an integer that is at zero by default, and can go up or down depending of circumstances (items, skills, roleplay ..)

• For a modified skill of zero, roll a (six-sided) die, succeed on a 4+

• For a positive modified skill of N, roll N extra die (N + 1 total), succeed if one of them is 4+

• For a negative modified skill of -N, roll N extra die (N + 1 total), succeed if all of them are 4+

I view more math games as definitely a good thing. I would think such a game would have to display its mechanics in such a way that the player can make judgments based on them, which would be so nice to have more of (being able to reason about what a game is doing without dropping to a debugger or something).

The more MoR-types of things that get out there makes it much easier for an average person to help raise the sanity waterline. People talking as much about the mechanics of various games versus talking about LW topics seems neat.

For what it's worth, I'm reminded of systems which handle modifiers (multiplicatively) according to the chance of failure:

[quote]

For example, the first 20 INT increases magic accuracy from 80% to

(80% + (100% - 80%) * .01) = 80.2%

not to 81%. Each 20 INT (and 10 WIS) adds 1% of the remaining distance between your current magic accuracy and 100%. It becomes increasingly harder (technically impossible) to reach 100% in any of these derived stats through primary attributes alone, but it can be done with the use of certain items.

[/quote]

A clearer example might be that of a bonus which halves your chance of failure changing 80% success likelihood to 90% success (20% failure to 10% failure), but another bonus of the same type changing that 90% success to 95% success (10% failure to 5% failure). Notable that one could combine the bonus first in calculation to get a quarter of 20% as 5% with no end change.

I think this is an excellent idea. I guess the simplest way to implement it would be to measure everything -- skills, character attributes, bonuses, task difficulties, etc. -- in decibels (or bits), and have a lookup table to convert the final log-odds value to die rolls.