Ai is able to memorize 5-number seqences. She is also able to use the numbers 1 to 9 in a limited fashion.
Adult humans are easily able to remember sequences of up to seven digits.
The Japanese researchers conclude that chimps are equipped with a similar, albeit limited capacity. Chimpanzees have a brain that is comparatively large among apes, roughly half the volume of the human brain. In remembering four-digit numbers, Ai achieved success rates of 90 percent. She was only right 65 percent of the time for 5-digit numbers. The probability of Ai picking the right numbers by chance lay only at 13 and 6 percent, respectively.