News Scientist, UK
12-03-07
Chimps outperform humans at memory task
Young chimps can beat adult humans in a task involving remembering numbers,
reveals a new study. It is the first time chimps – and young ones, at that – have
outperformed humans at a cognitive task.
And the finding may add weight to a theory about the evolution of language in
humans, say the researchers.
Three adult female chimps, their three 5-year-old offspring, and university
student volunteers were tested on their ability to memorise the numbers 1 to 9
appearing at random locations on a touchscreen monitor.
The chimps had previously been taught the ascending order of the numbers.
Using an ability akin to photographic memory, the young chimps were able to
memorise the location of the numerals with better accuracy than humans
performing the same task.
During the test, the numerals appeared on the screen for 650, 430 or 210
milliseconds, and were then replaced by blank white squares.
Photographic memory
While the adult chimps were able to remember the location of the numbers in the
correct order with the same or worse ability as the humans, the three adolescent
chimps outperformed the humans.
The youngsters easily remembered the locations, even at the shortest duration,
which does not leave enough time for the eye to move and scan the screen. This
suggests that they use a kind of eidetic or photographic memory.
In rare cases, human children have a kind of photographic memory like that
shown by the young chimps, but it disappears with age, says Tetsuro
Matsuzawa, at the primate research institute at Kyoto University, Japan, who led
the study. (See a video library of chimp cognition.)
He suggests that early humans lost the skill as we acquired other memoryrelated skills such as representation and hierarchical organisation. “In the course
of evolution we humans lost it, but acquired a new skill of symbolisation – in other
words, language,” he says. “We had to lose some function to get a new function.”
'Humbling' discovery
The finding challenges human assumptions about our uniqueness, and should
make us think harder about ourselves in relation to other animals, says
anthropologist Jill Pruetz of Iowa State University, Ames, US.
“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.”
The results are “absolutely incredible” says Frans de Waal, at the Yerkes Primate
Center at Emory University, Atlanta, Georgia, US. He says that chimp
intelligence is chronically underestimated, and one reason is that experiments
stack the deck against the chimps.
In the wild, this 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, he says.
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 are 98.77% chimpanzee. We are their evolutionary
neighbours.”