Counting chimp


Ayumu sits in front of a computer screen that displays the numbers from one to nine. His job is to sort these numbers into the correct order, and he does this to receive a bonus. Within a fraction of a second, the numbers are shrouded by white squares, so Ayumu must memorise the positions of the numbers. It sounds like a pointless and mundane office job, but in fact Ayumu is a chimpanzee.

Over the past few decades, researchers have begun to blur the perception that we are more intelligent than apes. Some have discovered, for example, that chimpanzees can use a switch to regulate periods of light and dark in a room (in order to sleep), crack open nuts with tools, and even recognise symbols. Indeed in this latter category, chimpanzees seem to show greater skill than humans.

The Ai project, currently headed by Professor Tetsuro Matsuzawa from Kyoto University, Japan, was set up to explore how chimpanzees understand symbols. It began in 1978, when scientists recruited a few chimpanzees, including a female called Ai, and taught them to recognise symbols. Positive reinforcement, in the form of a chime and pieces of apple, successfully ‘trained’ Ai and the other primates to recognise and order the numbers one to nine on a computer screen.

The story does not stop there. In an experiment measuring chimp memory, white squares masked the symbols after the first number had been picked. Matsuzawa’s team noted that Ayumu, Ai’s son, was better than his mother at remembering the positions of the numbers. In a further test, the numbers were shown for only a fraction of a second (just 210 milliseconds), before being masked by the white square. Again, Ayumu showed the greatest affinity among his primate peers for recognising the symbols, correctly remembering their positions and ordering them.

The researchers went further and decided to test Ayumu’s symbol recognition and memory skills against human participants. Perhaps unsurprisingly, human performance dropped as the time allowed for observation of the symbols decreased. However, Ayumu’s performance remained roughly constant – he was able to recognise and remember the symbols’ positions after just 210 milliseconds, observation time.

The researchers explain that this is due to eidetic imagery; the ability to retain a complex image at a high level of detail. Human children are able to do this, but we lose this ability as we age. In contrast, young chimps such as Ayumu seem to retain their ability for much longer, surpassing most humans. We often think of ourselves as mentally superior to primates, but clearly you should never challenge a teenage chimp to a memory game – the odds are biologically stacked against you.


IMAGE: Raul Lieberwirth

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