The Clever Hans effect: can animals really understand language?

“Reports of animals that could talk, read and even do complex calculations have appeared and reappeared over the years,” said Charles Seife on Slate. In early 20th century Berlin, a stallion named Clever Hans (pictured) became famous for answering questions and even doing basic arithmetic, by shaking his head yes or no, and tapping out numbers with his hoof. On closer examination, however, it emerged that Hans could only respond correctly when his owner, Wilhelm von Osten, a retired schoolmaster, knew the answer. Hans, it turned out, had been conditioned to pick up “subtle, involuntary cues” from his owner: when the horse had tapped out the correct number, von Osten would raise his head and the horse would stop tapping. Starting in the 1950s, a series of researchers taught sign language to primates, often adopting them and raising them like children. Linguists such as Noam Chomsky were sceptical: they suggested that the animals were merely learning to repeat the handlers’ signs in the correct context, usually in order to get food. An extended project undertaken in the 1970s with a chimpanzee punningly named Nim Chimpsky concluded that the ape had mastered 125 signs, but that this was not the same as learning a language. Nim was parroting back what his teachers were signing to him – a learnt reflex, albeit a complex one. In cases such as Koko’s, there is an extra complication: the ape’s instructor is often the only person able to translate for them. It’s hard to tell how much interpretation goes into that translation, particularly if they don’t share much evidence (Robert Sapolsky, the Stanford primatologist, has complained that Penny Patterson has published no data “you could actually analyse”). In videos, Koko often used the wrong sign – throwing in the word “nipple” randomly, which Patterson translated as she saw fit. Koko could certainly pair an impressive number of signs to the appropriate objects, said Molly Roberts in The Washington Post. “But when she signed ‘happy’ or ‘love’, did she really feel those things?” Or was that just what we wanted to think?