Clayton’s scrub jays today reside in an aviary in Madingley, a sleepy village outside Cambridge that hosts the university’s Sub-Department of Animal Behaviour. When I visited, evidence of their caching behavior was clear to see. They don’t just hide food: stones, corks and a nail had all been jammed between their enclosure’s wire mesh and its wooden frame. It was a while before I saw one of the birds bury an item of food — apparently my presence had interrupted the usual order of business. “Because you’re new, and they don’t know you, they are checking you out,” Clayton told me. I stared back, struck by the gulf between us. I’d read the scientific papers; I knew how cognitively sophisticated scrub jays are. Yet I experienced none of the emotional connection I have felt each time I have come face to face with a captive chimp.

Clayton, it seems, has no difficulties relating to her experimental animals. In part, she attributes this to a long-standing wish to fly. That motivated a lifelong devotion to ballet training, which she believes brings her as close as a human being can get to that experience. And she is convinced that spending much of her leisure time thinking like an artist made it easier to think about animal minds on their own terms. “We are limited by the fact that, as humans, we do see things in a particular way,” she says. “But that doesn’t mean we can’t try and minimize those constraints by taking ourselves out of the picture — which is what artists do all the time.”

Whatever the explanation, the discoveries from Clayton’s lab have come thick and fast. Recent experiments have exploited the fact that jays, like people, can get sated with one food item but still desire a different food type. (This is why we can still tuck into dessert even when we would turn down a second main course.) Working with a PhD student, Lucy Cheke, Clayton has found that even if Eurasian jays are sated on a particular food item, they will ignore their current desires and selectively cache that food if they have learned it is likely to be scarce in future. So now we apparently have jays planning ahead, in addition to acting on specific memories of the past.

It seems that jays also take account of the knowledge and desires of their companions. After male Eurasian jays watched their partners eat either waxworms or mealworms to satiety, Clayton’s team found that the birds selectively fetched the other food item for their partners. The males weren’t responding to some subtle “I want waxworms!” behavioral cue, because they only provided that preferred offering if they had actually seen their mates gorging on mealworms.

Earlier experiments with scrub jays had revealed that the birds change their behavior when they realize that their caches are likely to be pilfered. If watched by another scrub jay while caching, they later move their stashes around when given some privacy. Crucially, the birds only engaged in this crime-prevention behavior if they had themselves previously raided other scrub jays’ caches. Once they know from personal experience that stealing is something that jays can do, it seems that they then react accordingly when another bird’s knowledge about their caches poses a threat. Or, as Clayton puts it: “It takes a thief to know a thief.”

Together, these results suggest that jays possess something similar to what, in a human child, would be called a theory of mind — thinking about the mental states of others, and recognizing that they are autonomous beings with their own knowledge and motivations.