How a chimpanzee named Clint trained a psychologist to question human exceptionalism and reconsider the intelligence of apes.

The grape was out of his reach, and he pointed to it, making loud raspberry sounds (like a Bronx cheer), looking back-and-forth between me and the fruit. Now, you don’t need a PhD in experimental psychology to be able to interpret this signalling behaviour, right? However, without significant indoctrination into late 20th-century intellectual fashions you might not realise that Clint’s pointing was, at the time, theoretically impossible.