CHIMPANZEES – and young ones at that – have outperformed humans at a cognitive task for the first time. While chimps are not going to be winning any Nobel prizes just yet, the finding highlights the flexible nature of chimp intelligence and adds weight to a theory of the evolution of language.
Three adult female chimps, their three 5-year-old offspring and 12 university students were tested on their ability to memorise the location of the numbers 1 to 9, which appeared at random locations on a touch screen. The chimps had previously been taught the ascending order of the numbers. During the test, all the numerals simultaneously appeared on the screen for 650, 430 or 210 milliseconds, and were then replaced by blank white squares. Apparently using something like photographic memory, the young chimps remembered the location of the numerals more accurately than humans performing the same task – even at the shortest duration, which doesn’t leave enough time for the eye to move and scan the screen. Adult chimps remembered the location of the numbers with the same or worse ability as the humans (Current Biology, vol 17, R1004).
In rare cases, human children have a kind of photographic memory similar to that shown by the young chimps, but this disappears with age, says Tetsuro Matsuzawa of the primate research institute at Kyoto University, Japan, who led the study. He suggests that our ancestors lost the ability as we acquired other memory-related skills, such as hierarchical organisation. “In the course of evolution we acquired a new skill of symbolisation. In other words, language,” he says. “We had to lose some function to get a new function.”
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The study challenges the assumption that human intelligence is unique, and should make us think harder about ourselves in relation to other animals, says anthropologist Jill Pruetz of Iowa State University, Ames. “Observing that other species can outperform us on tasks that we assume we excel at is a bit humbling,” she says. “Rather than taking such findings as a rare example or a fluke, we should incorporate this knowledge into a mindset that acknowledges that chimpanzees, and probably other species, share aspects of what we think of as uniquely human intelligence.”
“Chimpanzees, and probably other species, share aspects of what we think of as uniquely human intelligence”
Frans de Waal of Yerkes National Primate Research Center at Emory University, Atlanta, Georgia, says the results are “absolutely incredible”. He says that chimp intelligence is chronically underestimated partly because experiments often stack the deck against the chimps. De Waal suggests that this particular memory skill might be useful for memorising fruit locations at a glance, or making a quick map of all the branches and routes in a tree.
Matsuzawa emphasises that the chimps in the study are by no means special – all chimps can perform like this, he says. “We underestimate chimpanzee intelligence,” he says. “We’re 98.77 per cent chimpanzee – we are their evolutionary neighbours.”
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