Integrating the Lindy Effect

post by lsusr · 2019-09-07T17:38:27.348Z · score: 15 (9 votes) · LW · GW · 5 comments


  Time t and Lifetime L 

Suppose the following:

1. Your intelligence is directly proportional to how many useful things you know.

2. Your intelligence increases when your learn things and decreases as the world changes and the things you know go out-of-date.

How quickly the things you know become irrelevant is directly proportional to how many relevant things you know and therefore proportional to your intelligence and inversely proportional to the typical lifetime of things you know . Let's use to denote your rate of learning. Put this together and we get a equation.

If we measure intelligence in units of "facts you know" then the proportinality becomes an equality.

The solution to this first order differential equation is an exponential function.

We must solve for . For convenience let's declare that your intelligence is at time . Then must equal . That gives us a tidy solution.

Our solution makes sense intuitively because your intelligence is directly proportional to and . But wait a minute. isn't just a coefficient. It's in the exponential too.

Time and Lifetime

Most human beings reading this article will be between 10 years and 100 years old. In other words, is measured in decades. In other other words, is on the order of 10 years.

values, on the other hand, are distributed exponentially across many orders of magnitude.

Order of days. (0.003 years)

Order of weeks (0.2 years)

Order of decades (10 years)

Order of centuries (100 years)

Order of millennia (1,000 years)

Order of 10,000 years

Order of gigaannum (billion years)


The details of whether exactly each of these things fit on the scale is not important. What is important is that most things you can know have a useful lifetime at least one order of magnitude away from the human timescale of decades. In other words, we can assume that either is much greater than or much less than .

Suppose is much less than . Then the exponential vanishes and we're left with . In other words, if then how long you have been learning for is irrelevant. I is constant with respect to time. Years and years of studying will not make you smarter over time.

Suppose that is much greater than . Then . What used to be a constant function becomes an increasing linear function.

grows with respect to time while stays constant. Eventually, anyone on an trajectory will always become smarter than someone on an trajectory even if the person on the trajectory has higher .

In the long term, the lifetime of things you learn is far more important than how fast you learn . Over a lifetime of decades, someone who learns a few durable things slowly will eventually become smarter than someone who learns many transient ones quickly.


Comments sorted by top scores.

comment by philh · 2019-09-13T14:20:38.025Z · score: 2 (1 votes) · LW(p) · GW(p)

(Note: your final equation has the << and >> swapped.)

comment by lsusr · 2019-09-30T17:57:34.101Z · score: 1 (1 votes) · LW(p) · GW(p)

Fixed! Thank you.

comment by lsusr · 2019-09-07T17:56:47.723Z · score: 2 (2 votes) · LW(p) · GW(p)

I'm not quite 100% sure if I can write or if I have to write or if there's some other scaling factor I'm missing. Please check my math.

comment by Pattern · 2019-09-07T19:34:07.078Z · score: 2 (2 votes) · LW(p) · GW(p)

Your writing suggests the second way is correct, not the first:

How quickly the things you know become irrelevant is directly proportional

[Emphasis mine.]

comment by lsusr · 2019-09-07T19:48:00.456Z · score: 2 (2 votes) · LW(p) · GW(p)

Thanks. This helps. I've edited my post to fix.