By Yudhijit Bhattacharjee
Most children practice this mental trick: When asked to wait patiently for a promised treat--say, an hour of television--they occupy themselves with a toy or a book. Researchers have now shown that chimpanzees engage in similar self-distraction, a finding that further blurs the cognitive and behavioral boundary between humans and other primates.
The discovery comes from a study conducted at Georgia State University in Atlanta. Psychologists Theodore Evans and Michael Beran put each of four chimps in front of a container connected to a candy dispenser. The chimps could reach over and pick up the container to eat the accumulated candies at any time, but doing so stopped the dispenser from delivering any more. That allowed the chimps to delay the reward as long as they wanted--so that they could get more of it.
In another experiment, the chimps were presented with the same scenario but also given some toys. Just like fidgety children, the chimps were able to hold out longer in this situation by distracting themselves with toys, the team reports online today in Biology Letters. To test whether playing with the toys was indeed a distraction technique, the researchers set up yet another condition in which the chimps could see the candy container filling up but couldn't reach it. Most of the chimps spent significantly more time playing with the toys when they could access the container than when they could not, indicating that their play was a deliberate strategy to control the impulse to eat the candies.
Frans de Waal, a primatologist at Emory University in Atlanta, Georgia, says the study fills yet another "mental gap" between humans and other species, adding to a list of impressive cognitive feats by animals such as the use of tools and planning for the future (ScienceNOW, 18 May 2006). "In humans, we'd certainly classify this as a form of self-awareness in relation to temptation: the knowledge that you'll fall for it unless you distract yourself," he says.
The authors say the study also suggests a more sophisticated self-awareness in animals than previously believed. "It makes us think about just how much of their own psychology chimps and other animals are aware of," says Evans. "Are the chimps aware that they are being tempted by the accumulating candies in the same way that some of us realize that items strategically positioned at the checkout counter tempt us to buy unnecessary goods?"