Working For Peanuts

The family of great apes, the orangutans, gorillas and chimpanzees, share almost all their genetic code with each other and us. I have even been told that men are genetically closer to male chimpanzees than women (because of the Y-chromosome), but I suspect that was more in the spirit of a put-down than a scientific classification.

Over recent years, we have come to respect their intelligence more and more. We never tire of devising new challenges for them in their captive environment. Hanus et al from the Max Planck in Leipzig have just challenged a group of great apes to compete with children at ages 4, 6 and 8 years old with “the floating peanut test”(1). Some of the apes were lab. captive and others were in sheltered accommodation in a reserves in Uganda and Indonesia. The children, on the other hand, were quite free-range and were coralled from local kindergartens and primary schools.

The test consists of a peanut in a clear acrylic tube strapped very firmly to the wall and the subject has to devise a means to retrieve it. They have access to water but no electric saws or drills.  The solution to the problem is to float the peanut out with water so they could eat it.

The gorillas didn’t cope with this at all. Perhaps a solitary peanut doesn’t look much like a treat to a large gorilla suffering from middle-aged spread. The other problem for the apes is that they had to carry the water in their mouth and spit it into the top of the tube. Rather difficult with a face shaped like an ape and a narrow tube strapped to a wall. They had to do a lot of supping and spitting to add enough water.

The Orangs were in a care Center in Indonesia and didn’t do well either. This was a surprise as a previous group in Leipzig had been quite good at it. 20% of the chimpanzees got their nuts.

So how did the kids do? They didn’t have to spit as they had water in a pitcher in the room. Well, the 4-year olds didn’t do as well as the chimps with only 8% getting their nut. Six year olds did better with a 50% success rate. This rate increased to nearly sixty percent with 8-year olds.

My question is why did 40% of 8-year olds fail? Was the reward too small and their expectations too high?


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