Rhesus Macaques are Statisticians

There’s new research coming out from Nature that shows us rhesus macaques are really tuned into statistics and probabilities, they may even have neurons specialized to calculate probabilities. Macaque IllustrationBut don’t get your hopes up too high… these monkeys will not be your bookies or be crunchin’ gout some gnarly ANOVA tests with p-value significance.

What you can expect, and this is all paraphrased from a New Scientist news article on this research, is what authors Tianming Yang and Michael Shadlen from Howard Hughes Medical Institute and the University of Washington have reported. They tested the reasoning capabilities of two rhesus macaques,

“By showing them a series of abstract shapes on a video screen, the monkey saw a sequence of 4 of 10 possible shapes then, had to choose which target to look at. The probability that the red target would give the reward was the sum of the probabilities for each of the four shapes; otherwise, the green target yielded the drink… both macaques learned to match their choices closely to the actual probabilities revealed by the shapes they saw, choosing the correct target more than 75% of the time.

This is the first time monkeys have been shown to make such subtle probabilistic inferences.”

Yang and Shadlen observed neurons responding to the first shape,

by firing at a rate proportional to the probability suggested by that shape. As each successive shape was shown, the firing rate changed to match the probability determined by all the shapes seen so far.

“We’re seeing neurons that are making computations,” says Shadlen. In particular, the neurons appeared to be computing the log likelihood ratio of red versus green rewards – exactly the sort of computation a statistician might do.

Like I said above, the results are published in Nature, “Probabilistic reasoning by neurons.” Hat tip to Afarensis for pointing this study out in his blog.

2 thoughts on “Rhesus Macaques are Statisticians

  1. Any ideas on how these findings compare to previous studies of great ape reasoning abilities? Or more specifically, are these rhesus macaques demonstrating abilities that have not previously been seen in any non-human primates?

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