Tetsuro Matsuzawa begins his working day, conventionally enough, in front of a computer. He taps in a few commands, takes a seat and waits. Within minutes, the calm of his basement laboratory is pierced by the sound of excitable primates.

On cue, two chimpanzees appear through an opening in the ceiling, flash a look of recognition at Matsuzawa, and then aim an inquisitive stare at his unfamiliar companion from the Observer.

Matsuzawa feeds them a spoonful of honey each and wipes their hands and fingers – a near-daily ritual meant to reward them for arriving on time, and to encourage them to show up again the following morning.

After all, Ai, a 36-year-old chimpanzee, and her 13-year-old son, Ayumu, are free to stay in their nearby home, a re-creation of a west African rainforest they share with 12 other chimps. That they are such willing participants in Matsuzawa's experiment is a tribute to the bond that has built up between the professor and the chimps during many years of research.

Over the course of more than three decades, Matsuzawa, a professor at Kyoto University's Primate Research Institute in Inuyama, a historic town in central Japan, has gained unprecedented insights into the workings of the primate mind, and by extension, our own.