Linguists and philosophers such as Noam Chomsky and Steven Pinker argue that rational thought is impossible without words or other symbolic forms of language. In our last post, we suggested that Imo the macaque was a monkey genius because she was able to invent novel, effective solutions for cleaning dirty food. Imo obviously had no formal symbolic language, so Chomsky and Pinker would have to argue that she could not think rationally. But such an argument leads to a paradox. Either Imo was able to innovate without thinking - in which case we also have to question whether human innovators need to be rational inventors - or there are forms of effective thinking that do not involve words - in which case rationality is not limited to those who can use symbols. We favor the latter possibility.

So what would non-symbolic rational thought be like? Here's a primate puzzler which involves no words or mathematical symbols at all. And its solution suggests that apes can be just as intelligent as any human being at certain tasks - and maybe more so!

To set up the puzzle, you need to know a few facts. Back in the 1920s, a famous psychologist named Wolfgang Koehler began studying the intellectual abilities of primates such as chimpanzees. He posed the apes various problems such as obtaining food that was out of their reach beyond the bars of their cages. He also supplied the apes with various lengths of stick, none of which were long enough singly to reach the food but which might be easily assembled to pull the food back into the cage. The test was to see whether the apes would be clever enough to realize that the sticks could be used as tools, and then put the sticks together to make one long enough to do the job. Many did.

Another one of Koehler's famous experiments involved hanging a banana from the ceiling of a room, out of reach of a group of chimpanzees. Scattered around the room were wooden crates of various sizes that, if stacked, could provide a platform high enough for the chimps to secure the food. Again, many of the chimps succeeded. We're sure that you would have, too. Without a doubt every one of us would have assembled those sticks or stacked those boxes every bit as quickly (or more quickly) than our primate cousins.

But now for the chimp challenge - and the puzzle that can give a human being a bit more pause than an ape. It is said that one day, just after Koehler had hung a banana from the ceiling of the chimp's room, but before he had brought in the crates, one chimp managed to get the banana. How did the chimp do it?

Still scratching your head? We'll give you some hints: the chimp didn't jump; the chimp didn't beg; there was no ladder or chair in the room. There's just Koehler, the chimp, a room, and a banana.

We'll give you one more hint: "think" about how you would have solved the stick and crate problems described above. Would you have used words? Equations? Or what? It's that "what" that is the clue to solving this puzzle. And it's this "what" that we'll be exploring in our next few blogs (in which we'll also give you the answer!).

© Robert and Michele Root-Bernstein 2012

Chimpanzee images from: Wolgang Köhler: The Mentality of Apes (New York: Harcourt, Brace & Company, Inc., 1926). An excerpt of the book is available online at: http://www.pigeon.psy.tufts.edu/psych26/kohler2.htm

Videos of Koehler's experiments with the chimps are available at:
http://ematusov.soe.udel.edu/cultures/german_gestalt_psychologist...