As the saying goes, if you put 100 monkeys with typewriters in a room long enough, you’ll get Hamlet. That’s not true, but apparently if you put some rhesus monkeys in a room with numbers and reward them for choosing the right one long enough, you can get them to do math.
Harvard Medical School professor Margaret Livingstone’s experiment used positive reinforcement in the form of rewards “drops” to teach rhesus monkeys to understand the numbers 0-25. Livingstone presented the monkeys with a choice between two numbers, and rewarded them with the number of drops that corresponded with the number they chose. To get a bigger reward, they had to identify the bigger number.
There have already been examples of animals having a sense of numbers and value, but Livingstone’s work went further, and when the monkeys learned 0-25, she presented them with a choice between one number or two. The early results showed that the monkeys would pick the single number if it was larger than either of the two numbers. For example, if they were given a choice between “8” on one side and “7 and 5” on the other, they would choose the 8, since it’s larger than 7 or 5.
Eventually, they learned that the combination of two numbers could be greater than a single number. They realized 7 +5 is greater than 8, and learned to choose the larger reward 90% of the time according to Livingstone’s report in The Proceedings of the National Academy of Sciences. Livingstone also noted that the monkeys were more likely to choose the lesser reward if there was a larger number in the pair. So, they’d be more likely to choose wrong with “8 or 7+4” than “8 or 5+6,” because the 7 is larger than the 5 or 6.
So, monkey math isn’t perfect, but we’re willing to bet 90% is a higher success rate than a lot of small human children are capable of, so it’s still really impressive.
(Margaret Livingstone via I Fucking Love Science, image via Anne-Lise Heinrichs)
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