Other chimps were divided into three groups. Some were teamed up with Erica, who lifted the block. Others went with Georgia, who poked the block. And others were left to figure it out for themselves.
Erica and Georgia weren't teaching the other chimps, Horner says. They were simply trying to get lunch while others watched. And it turned out that in each group the others not only watched, they learned precisely how to mimic their elder and get at the food. Each group of 17 chimps had only one failure, possibly because one loser ranked so low in community standings that he or she never got a chance to try it.
As for the chimps in the third group, deprived of a leader who knew the rules of the game, none of them succeeded.
And at that point the experiment might have ended, except for a twist that came as a bit of a surprise to the researchers. It shows that conformity is a powerful force indeed, even among chimps.
It turns out that poking was a more natural way of getting the food than trying to lift the block. It's a bit more "chimpy," as Horner puts it.
In the wild, chimps use sticks to poke into ant colonies to get at the ants, and it's a pretty easy thing for them to do.
So it wasn't a surprise when some of the chimps that had learned how to lift the block to get the food soon learned an easier way. Poke it instead.
But here's the surprise. They didn't stick with it. Instead, after experimenting with poking, they returned to the method they had learned from their elder, even though it wasn't the "chimpy" thing to do.
The researchers think their experiments demonstrate two things. Chimpanzees do, indeed, develop distinct cultures that are very persistent, probably even transmittable to their offspring. And they want to fit in with the rest of their group, so they conform, even if they have figured out a better way to get the job done.
Doesn't that sound, well, so human?
Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.