Nicky Clayton: What makes certain animals so clever?

In this edition of Titans of Science, Chris Smith speaks with expert in animal comparative cognition, Nicky Clayton...

Chris - But these are uncanny abilities. What endows, if we look inside the brain, these birds with these abilities, is their brain different in some way or special in some way compared to other animals that can't do this? What sets them apart?

Nicky - Corvids in general, so crows and rooks and jays and magpies and ravens, have huge brains for their body size. So their brain relative to body size is as big as that of a chimpanzee and other non-human great apes. We also know that the areas of the brain that are enlarged in these birds are the same areas that are sought in mammals, especially in apes, to be key for cognitive ability. So it's the medial temporal lobe for memory and it's the prefrontal cortical areas and the visual cortex, all of which are really important for memory perception, future planning, metacognition. So being able to reflect on your thoughts, think about your memories, assess your plans of what you want to do in the future. Those are the areas that play a critical role. And they're the bits that are so enlarged in these birds. And you can say, well maybe relative brain size isn't ideal. I mean, of course they're going to be light because they need to fly. If you need to fly, you want hollow bones and you lack teeth and everything else. So maybe it's just that you've got very light bodies for your brain size. But if you look within birds and you were to compare a rook or a crow with a pigeon, all the birds are about the same body size. The corvid brain, the rook and the crow brain, is about four times the size of the pigeon brain. And when you look at which bits that are enlarged, it's all these areas that are involved in cognition in humans.

Chris - What do you think has driven that? Because whenever you ask a question about evolution, the answer is always, well because it's been selected for, it must confer some kind of advantage. But what do you think are the pressures that have made this group of animals have these abilities?

Nicky - I think the selection pressures involved in the evolution of intelligence for great apes and corvids are the same and they're probably of two kinds. The first is being long lived with a highly complex social life. And I don't mean just going around in a big group. The interactions I have in rush hour on the London tube are not cognitively social <laugh>. It's just a crowd. However, the kind of interactions you have at a dinner party in college for example, or a university debate or a political debate where you are actually talking with one another and discussing ideas. It's those kinds of complex social interactions, surviving the trials and tribulations of life, figuring out who are your competitors and who are your collaborators, those kinds of things. So that's one big selection pressure and I think that is true of both the great apes and the corvids. And then the other one is physical and that comes in two forms, really. It's time and it's tools. It's time because it's keeping track of when foods are ripe and when they perish. So in the case of the many of the primates, it's about ripening fruits because fruit trees reveal fruit, but at some stage it's not ripe and it's inedible, at some times it's ripe and condition and then it gets over ripe and it's no longer edible. In the case of the corvid, it's mainly in the form of worms and probably olives as well, things like that. But they too perish. So it's keeping track of time and knowing when to find things in tip top condition. And then the other one is tools. So the ability to not just use tools, but also to make them and understand what kind of tool will be useful for what. So in the Aesop fable example we started with, understanding that the kind of tool that you use is critical because a really light one won't displace the water at all. A really big one, provided it fits in the tube, will be much more efficient at raising the water level than adding in many tiny little pebbles.