March, 2006: My three year old son sat at one end of a table in the psychology lab, excitedly shaking a tiny green truck sealed inside a Plexiglas tube. The game he was playing was simple: if he could get the truck out of the tube, he got to keep it. He’d already ‘won’ two toys – a small Koosh animal he’d had to push out of the tube with a snug-fitting rod, and a toy bug he’d retrieved from the far end of the table with a rake. But this time the rod was a couple of feet out of reach, and the rake’s handle was too fat to fit inside the tube. After a few minutes of shaking and poking, he grabbed the rake, pulled the rod across the table, and pushed the truck out of the tube. Score three for Robin; another data point for the graduate student running the experiment.
Cognitive scientists think that the ability to use one tool to retrieve another is closely associated with the brain’s ability to reason and plan. Obviously, people can do it -- although the ability doesn’t develop until late in toddlerhood -- but there’s evidence that it isn’t a uniquely human behavior. Placed in a situation where they need to use one tool to reach another in order to retrieve food, some individual gorillas, chimpanzees, orangutans, and capuchin monkeys solve the “two tool” problem without coaching. And more recent research suggests that some birds are in on the act, too. Take a look at this video from the University of Oxford, in which a New Caledonian crow (Corvus moneduloides) named Betty chooses not two, but three tools in a row –successively using a shorter stick to pull out a longer stick until she gets one that’s long enough to reach her treat.
Betty had already learned how to use the sticks to pull food out of tubes, but this test was the first time she was faced with a situation that called for using different-sized sticks in a set sequence. Which, interestingly, made it remarkably similar to the test my son took when he was three. Both bird and boy got simpler tool-using tasks to complete before they were faced with a more complex multi-step problem. Since his test, the boy has moved on to master even more complex puzzles – these days, he’s not just retrieving toys, he’s building three-dimensional models of spaceships in Legos. I’m still impressed by the bird.
Reference: Wimpenny, J. H., A.A.S. Wier, L. Clayton, C. Rutz and A. Kacelnik 2009. Cognitive processes associated with sequential tool use in New Caledonian Crows. PLoS ONE 4(8): e6471.
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