Chimps have for the first time been shown to pass knowledge from one individual to the next with nearly perfect accuracy through several 鈥済enerations鈥� of teacher and learner. This ability means that these apes have one of the key skills needed to create and maintain cultural differences between groups.
It has been known for many years that different groups of wild chimps behave differently, but it remained uncertain whether these behaviours represent adaptations to subtly different conditions or different traditions inherited culturally within each group. To find out, Victoria Horner, a primate behaviourist at the University of St Andrews in the UK and the Yerkes National Primate Research Center in Atlanta, Georgia, and colleagues set up a controlled experiment to test whether chimps are capable of transmitting knowledge faithfully through a chain of learners.
Horner and her team devised a box whose door could be opened in either of two ways: by lifting a flap or sliding it sideways. Then, says Horner, 鈥渨e basically set up the telephone game with chimpanzees.鈥� The telephone game, also known as Chinese whispers, tests how a message changes as it is passed along a chain of people. In this case the 鈥渕essage鈥� was how to get at a food reward hidden behind a flap. The team trained one chimp to lift the flap to get at the food, then let a second chimp watch the first one demonstrate the technique several times. The 鈥渢eacher鈥� was then removed, a new naive apprentice was brought in to watch the newly taught chimp, and so on. A second cultural lineage was begun with a chimp trained to slide the door instead of lifting it.
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In both lineages, the knowledge was passed down almost perfectly: through six teacher-learner generations, chimps trained by lifters always lifted, and through five generations sliders always slid (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0606015103). The researchers observed only one error, a slider that lifted once out of 20 trials, but its apprentice learned to slide anyway.
鈥淚n both lineages, knowledge was passed down almost perfectly through at least five teacher-learner generations鈥�
The result shows that cultural learning is strong in chimps, says Horner. 鈥淚f the chimps weren鈥檛 learning from each other, we鈥檇 expect over a couple of generations it would degrade to a 50:50 performance. If they weren鈥檛 very good at copying, you wouldn鈥檛 see this almost 100 per cent accuracy.鈥�
