A Japanese research institute confirmed that Ai, the famous female chimpanzee from the Primate Brain Research Project—an emblematic study of primate cognition and memory—has died of old age at 49.
On 13 January 2026, Japan’s Kyoto University’s Center for the Evolutionary Origins of Human Behavior announced that Ai, a female chimpanzee renowned for her intellectual abilities, passed away on 9 January at age 49 due to old age and organ failure, with caregivers by her side in her final moments.
Ai was born in West Africa and brought to the Japanese institute in 1977, later becoming the central figure in the "Ai Project," a world-leading research on chimpanzee cognition led by renowned primatologist Professor Tetsuro Matsuzawa.
Research showed Ai could use numbers and distinguish colors. Researchers provided her with a special computer-connected keyboard from just 18 months old to study memory and learning. By age five, Ai was proficient in naming numbers from 1 to 6 and could identify numbers, colors, and objects from over 300 samples.
Beyond intelligence tests, Ai was also famous for drawing and coloring, often enjoying using markers to create on blank paper without food rewards typical of other experiments. Her passing is regarded as a significant loss to primate research and a notable chapter in the history of studying cognitive abilities in animals closest to humans.