Animal cognition

When Descartes suggested that nonhuman animals are machines, he made formal a view widely taken for granted by most thinkers in the Western tradition. In the process, he conveniently supplied a rationale for the curious assumption that only humans have souls. (Swimming against the tide, Saint Jerome argued in the early 400s that certain animals might have small souls.) Darwin's theory of evolution by natural selection licensed a new take on the problem: the difference between human and animal mentality was more likely to be one of degree. His enthusiastic followers began to discover that other species are very clever indeed. G.J. Romanes, in his Animal Intelligence (1882) found thought in virtually every creature from insects to mammals, but was especially impressed with primates. By 1900, the flood of smart-animal stories reached flood stage. Theodore Roosevelt and the well-known writer John Burroughs took on what they called the Nature Fakers, who fudged the truth between fiction and fact. They mounted a blistering attack, for instance, on William Long's story of a woodcock that set its own broken leg using a cast made of mud. During the height of the debate came a gentle German schoolmaster and his famous pupil, Clever Hans. Hans, a Russian trotting horse, had learned the rudiments of addition and subtraction. He was known to read and spell, compute fractions and tell time, understand music and calculate dates. He tapped out most of his answers, but could also respond by pointing his nose. Many notable experts observed Hans and questioned him with remarkable success, even in von Osten's absence. A panel formally appointed to investigate concluded that no trickery could be involved, but the members were quite reasonably worried that Hans was rather too clever. They engaged the psychologist Oskar Pfungst to study the horse further. Using a double-blind technique, Pfungst discovered that Hans was 'reading' the tension in his audience: when he reached the correct number of taps, the observers unwittingly relaxed. Animals like Hans learn, but what does this ability to benefit from experience tell us about cognition? Does the learning involve understanding? Ivan Pavlov stumbled on the apparent key to this facet of the animal mind in 1903 in the course of his studies of digestion. He found that, once they had learned a predictive cue, dogs would begin salivating for food before it appeared. The dog innately recognizes food by an unconditioned stimulus, …