Tetsuro Matsuzawa begins his working day, conventionally enough, in front of a computer. He taps in a few commands, takes a seat and waits. Within minutes, the calm of his basement laboratory is pierced by the sound of excitable primates.
On cue, two chimpanzees appear through an opening in the ceiling, flash a look of recognition at Matsuzawa, and then aim an inquisitive stare at his unfamiliar companion from the Observer.
Matsuzawa feeds them a spoonful of honey each and wipes their hands and fingers – a near-daily ritual meant to reward them for arriving on time, and to encourage them to show up again the following morning.
After all, Ai, a 36-year-old chimpanzee, and her 13-year-old son, Ayumu, are free to stay in their nearby home, a re-creation of a west African rainforest they share with 12 other chimps. That they are such willing participants in Matsuzawa’s experiment is a tribute to the bond that has built up between the professor and the chimps during many years of research.
Over the course of more than three decades, Matsuzawa, a professor at Kyoto University’s Primate Research Institute in Inuyama, a historic town in central Japan, has gained unprecedented insights into the workings of the primate mind, and by extension, our own.
In a landmark test of short-term memory conducted in public in 2007, Ayumu demonstrated astonishing powers of recall, easily beating her human competitors, who had been in training for months.
The strength of Ayumu’s cognitive functions surprised even Matsuzawa, who has studied the mental dexterity of chimps for 36 years. He makes long annual visits to Bossou in south-eastern Guinea, where he witnesses chimps display in the wild the same powers of recognition and recall that Ayumu and other young chimps demonstrate on his computer screens.
“We’ve concluded through the cognitive tests that chimps have extraordinary memories,” Matsuzawa says. “They can grasp things at a glance. As a human, you can do things to improve your memory, but you will never be a match for Ayumu.”
The results stunned observers. In the tests, Ai and Ayumu, and two other pairs of a mother and offspring, were shown the numerals 1 to 9 spread randomly across a computer screen.
Their task was to touch the numbers in ascending order. To complicate matters, the game was altered so that as soon as the chimps touched the digit 1, the remaining eight were immediately masked by white squares. To complete the exercise, they had to remember the location of each concealed number and, again, touch them in the correct order.
In an even harder version, five numbers appeared on the screen before turning into white squares. The animals and their human counterparts displayed the same degree of accuracy – about 80% – when the numbers remained visible for seven tenths of a second. But when the time was reduced to four tenths of a second, and then just two tenths, Ayumu maintained the same level of accuracy, while his mother and the human volunteers floundered.
Given that humans share 98.8% of their DNA with chimpanzees, why do the latter have such vastly superior working memories?
The answer lies in evolution, says Matsuzawa. As humans evolved and acquired new skills – notably the ability to use language to communicate and collaborate – they lost others they once shared with their common simian ancestors. “Our ancestors may have also had photographic memories, but we lost that during evolution so that we could acquire new skills,” he says. “To get something, we had to lose something.”
For the chimps, the ability to memorise the location of objects is critical to their survival in the wild, where they compete for food with other, often aggressive, ape communities. To thrive, an individual chimp must be able to look up at, say, a sprawling fig tree and quickly note the location of the ripe fruit.
“They have to be able to think quickly because there are other hungry chimps behind them,” Matsuzawa says. “They have to grasp the situation as quickly as possible and decide where to go.”
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