Working memory, the brain’s mental sticky note, lets us briefly hold and juggle information, like a phone number we’re dialing or the positions of chess pieces mid-game. Most adult humans can track about seven items at once before details start to slip. In 2007, a group of chimpanzees in Japan proved just how far behind we might be.
The star of the experiment was Ayumu, a then-7-year-old male chimp who seemed to treat the task like a game. His photographic precision left researchers stunned: he could recall the exact location of all nine numbers after seeing them for just 650 milliseconds, less than the blink of an eye. Humans given the same test, with months of practice, still lagged far behind.
Why the edge? One theory points to an evolutionary trade-off. Humans may have sacrificed some working memory capacity in exchange for advanced language and abstract reasoning. In the wild, a chimpanzee’s survival hinges on razor-sharp spatial and short-term recall: remembering where ripe fruit is hidden in dense foliage or the exact location of rival group members. For humans, whose lives became less dependent on immediate recall, that capacity may have quietly eroded over millennia.
Today, Ayumu’s performance is a humbling reminder: our species isn’t the undisputed champion of every mental arena. While we’ve built rockets and written novels, some of our closest relatives still beat us in pure, fleeting recall.
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