[ Question ]

Inaccessible finely tuned RNG in humans?

by Sandi1 min read7th Oct 202012 comments

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NeuroscienceGame TheoryWorld Modeling
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It was my impression that humans are bad at random (number) generation. Tell a person to arrange stars on a black canvas randomly, and they'll space them out more or less equidistantly and uniformly. If asked to generate a sequence of coin flips, we would avoid longer runs of the same coin face, which do happen with real coins.

The scientific consensus agrees. Here's a study where participants are asked to generate a sequence of 300 digits from 1 to 9. The researches successfully predict the next digit with a 27% chance (a truly random sequence would indicate an 11% chance). Scott Aaronson designed a simple program that predicts which of two keys the user will press next with a 70% chance on average.

On the other hand, I've seen a number of informal online polls (e.g. on reddit and twitter) where the respondents demonstrate an ability to randomly sort themselves into two groups with a very high degree of accuracy. See here and here, though I've seen a ton of these with various ratios. I've never seen it not work. It does break down for 1-99, but that seems reasonable to me.

The question is, do you know of any research into this phenomenon or do you have a good explanation for it?

Note that the ability is there in some contexts but not in others. An RNG exists within us, but our access to it is sometimes blocked. I've seen other examples of this in psychology so it doesn't weird me out as much as it used to, but I still wanna point it out. 

If this seems like a queer phenomenon to fixate on, know that an RNG is useful in many contexts. It's necessary for strong/optimal strategies in certain games (poker, rock paper scissors) and game theoretic scenarios. It's useful for coordination without communication. The best known algorithms for some problems are probabilistic.

And while I have your attention: https://www.strawpoll.me/21064106

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3 Answers

Getting a single random choice (e.g., of poll options) and getting a random sequence (e.g., of numbers, or coin faces, or star locations) are different tasks. Perhaps the problem isn't that people can't make an approximately random choice; it's that they can't make independent random choices. That's why people place the stars equidistantly or avoid repetitions. Having already placed the first star, or already said "Heads", we don't know how to forget. The second star, the second flip, is chosen in a different mental context: not in an unmarked uniform space, but in a space that already has a star on it.

Generate several "random" numbers in your head, trying to generate them randomly but falling prey to the usual problems of trying to generate them in your head. Then add them together and take them mod X to produce a result that is more like a real random number.

It seems fairly easy to get a sequence of random-seeming numbers by e.g. applying some transform to the first ten digits of pi if you remember those, your birth date, other important dates, etc. As long as you come up with a procedure to convert to the scale you need, it shouldn't be predictable for low sample sizes. 

300 random numbers is pushing it, though. For that you'd need a hash function, which most can't calculate mentally without specific training.