Titans of Science: Nicky Clayton

What the smartest animals are, and what makes them so smart...
02 July 2024
Presented by Chris Smith
Production by Rhys James.


Nicky Clayton


In this edition of The Naked Scientists: How clever are birds really? Titans of Science continues, as we sit down with Cambridge University psychologist, and expert in animal comparative cognition, Nicky Clayton.

In this episode

A rook

Nicky Clayton: Are crows as smart as children?
Nicky Clayton, University of Cambridge

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

Chris - Today I am at Clare College to meet Nicky Clayton, professor of comparative cognition at the University of Cambridge and also a fellow of the Royal Society. Nicky's dedicated much of her life to the study of the cognitive performance, behaviour and problem solving abilities of corvids, they're members of the crow family. She graduated with a degree in Zoology from the University of Oxford in 1984 before she embarked on a PhD at the University of St. Andrews. It's Nicky's work on animal cognition as well as cognitive development in human children here in Cambridge. That's made her a leader in the field. Nicky, you've pioneered this field of how birds think. Why did that attract you in the first place? Why did you go into that?

Nicky - I always wanted to be a bird. I've got invisible wings. That's why you can't see them. And it's my passion and fascination for birds that drew me to both science and the arts. I wanted to move like a bird and that's what drew me to ballet. And then later in life, other forms of dance and my long standing collaboration with Mark Baldwin, OBE. But it also drew me to science because I wondered what lies behind that beady eye. What do birds think about and how do they do it without the linguistic narrative structure that we take for granted?

Chris - They do have a language of sorts though, because they seem to one another.

Nicky - Yes, they certainly communicate and they're very vocal. We can hear some blackbirds singing in the background and a couple of great tits actually. But whether it's language in the way humans use language is another issue because we have words that have very specific meanings with a very tight grammatical structure. So for example, if I say 'A loves B', it doesn't necessarily follow that 'B loves A'. Although it's interesting because recent work not done by me, but colleagues in Germany have shown that crows are able to verbalise numbers and count. So yes, there is some evidence that they do have some kind of rudimentary linguistic skills. And in our lab, one of my PhD students, Francesca Cornero, has been working with our superstar rook. His name is Leonidas, Leo for short. And he responds to human commands in the way that dogs do. But unlike dogs, he's not domesticated. So he can do come here, he can do speak, and he goes 'rah rah rah' in rook style. He can do stay and wait and fly up. So he responds to human commands and from different humans. So it is interesting that there are some linguistic skills and it's certainly true that vocal learners in general, so songbirds, hummingbirds and parrots seem to be particularly intelligent.

Chris - If birds could sit an IQ test like we do for humans, what IQ would we give them?

Nicky - Well, that's a good question. Obviously, if we are talking about language one thing's for sure. They can't read and write. So there's no point asking them to sit at a desk. They could perch that wouldn't be a problem. Holding a pencil and a beak is probably all right as well. But the reading and writing bit, I fear is a non-starter. So I suppose really you start with problem solving tasks. And I've always thought that the important thing was to pick behaviours that they naturally do for a living so that you tap into their natural talents. And that I suppose has been the approach throughout my career. I've studied many different species of birds, many of them but not exclusively corvid. But I've always thought to look at natural behaviours that they do for a living and use those to see if you can tap into their cognitive abilities.

Chris - How old would a child have to be, though, in order to do some of the things that you found these birds are capable of working out how to do and doing?

Nicky - Well, it depends on the task. One example comes from one of Aesop's fables. And I do wonder whether Aesop's fable had some fact to it originally, but the fable is called the crow and the picture and the story is that as this crow is thirsty and it encounters a jug of water and it wants a drink from the jug because that's the only water source currently available. But it can't reach the water because the water level's too low. And so it gathers up some stones, plops them into the picture, raising the water level in the jug, therefore enabling it to drink. Well, we've done similar tasks with our corvids. We've looked at rooks and we've looked at Eurasian jays and New Caledonian crows and they all do it. We don't make them thirsty. That seems a bit cruel. It's fine if a bird happens to be thirsty. But in the lab we bribe them using wax worms. And for children actually we bribe them using stickers, <laugh> and the stickers say 'University of Cambridge, I'm as clever as a crow'. And the children love them because they can't get these fancy stickers anywhere else. So it's bribery, but it's not a cruel kind of bribery.

Chris - The birds can do this if you give them a challenge like the Aesop fable trying to get to the water, they naturally seem to know, in inverted commas, how to raise the water level by dropping something in. And that will displace water upwards.

Nicky - So we give them stones and what we find is that once a stone has accidentally been knocked into the tube, they then start adding stones to the tube to raise the water level. We know that they don't put stones in the tube if the tube is full of sand instead of water. And they don't put stones into the tube if it's full of air rather than water. So they seem to understand that it only works with water. First trial, so they instantly know it. And then you can give them a choice of objects to put in the tube with water. And they deliberately choose the heavy ones that raise the water level, not the ones that sink. And I've got wonderful videos of this and the audience can probably see some of these on YouTube or on BBC cleverest animal footage where Romero, one of my rather handsome gentleman Eurasian jays, he's rather gorgeous darlings, and he loves to put the stones in. But if he puts an item that floats in, he immediately removes the offending article and then focuses on the stones to raise the water level to get his delicious wax worm.

Chris - Is it just weight or do they also know that displacement is proportional to the volume? So if they put something that will sink but has a big volume, it's going to displace more water and push the level up so it takes them less time. Do they get that?

Nicky - Well, I don't think they've been trained on Archimedes' principle to be fair. However, yes, they do get it. So they only add in the number of stones they need to raise the water level and they don't need to have felt the stones beforehand. So in one experiment, which we called the fan experiment, they could simply see or infer which ones were heavy and which ones were light based on the way they moved in the wind. So obviously the light ones blew all over the place and the heavy ones didn't. And they instantly then went for the heavy ones to raise the water level. And we did the same thing with kids, with children, except obviously we didn't put wax worms on the top. I don't think the children would've been very interested in those. We had little stickers that float and the little stickers that float could then be exchanged at the end if they got a sticker for this really fancy posh sticker that said, I'm as clever as a crow. And children didn't pass the task until they were eight years of age.

Chris - Wow. So that would put the bird reasoning at the level of maybe an 8-year-old? In some respects,

Nicky - Yes, in some respects. Because I always think we have to be a bit careful. There are many ways in which they're not like 8-year-old children. They don't have hands, for example. They do have wings. Most children do not. Although as I told you I have invisible wings. But that's another story. But it does give you an indication that some of the cognitive capacities that they seem to have are really quite sophisticated ones that develop relatively late in childhood, at least in our species.

Chris - Not to mix metaphors, but are there one trick pony on this? Is that all they can do or do they also display uncanny cognitive powers in other domains as well?

Nicky - They can do all kinds of other things. So there are observations in the wild, for example, of rooks on the Membury service station on the M4 being able to work in cooperative teams to pull up the bin liner under their feet. And then they have two working in tandem at opposite ends of the bin. And then they start chucking the food out of the bin. And then once one of them has a good grip of most of the food, the other hops down to the floor to guard the food so that the blackbirds and wagtails and starlings and other birds around can't steal their stash of delicious treats. And then they just keep chucking them out. But it takes about 20 or 25 pulls before you even get to the right level of the bin where the food is. So it shows a sense of time, of persistence, of self-control. It's not just 'I pull it, I get food, I'll keep pulling'. It's not simply trial and error learning or one trial learning as it's sometimes called. They've really got to plan ahead to do this. So it takes time, it takes teamwork because you need at least two to stand at either end of the bin to do it. And of course it's an understanding of tools. They're using the bin liner as a tool with which to get the food. And although they don't use tools habitually in the wild New Caledonian, crows and Hawaiian crows do. But most of the corvids don't use tools in the wild. And yet all the ones I've worked with readily use and manufacture tools in the lab. We think they don't use them in the wild because they don't need to. If I lived on a diet of soup apples and potato crisps, I wouldn't use tools either. I could drink my soup, I could bite into my apple and using a knife and fork or some chopsticks for crisps would be a really rather stupid idea methinks. Not that that's my diet, it probably wouldn't be too healthy. But you know, I

Chris - Don't think you're doing your dancing much good if you lived on that.

Nicky - Well that's true. Yeah. You know, you don't see many obese ballerinas now do you <laugh>


Nicky Clayton: What makes certain animals so clever?
Nicky Clayton, University of Cambridge

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.

Eurasian Jay

Nicky Clayton: Can animals plan for the future?
Nicky Clayton, University of Cambridge

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

Chris - When we first met, and this is quite a while ago now, you a turned up with a whole load of Robbie Burns's poems and you read them on the radio because you were referring to the fact that you'd just done a study on this whole question of planning for the future and having a sense of time. Because that, and I've quoted you on this so many times because it made such a huge impression on me when you did that study, because you were able to show these animals experience something, realise what it's telling them, and extract the right information to then know how it should inform their future behaviour. And they do it very quickly. Talk us through that study again because it's fascinating.

Nicky - Sure. So we called it the 'Planning for Breakfast Experiment'. And the history behind this is that many people assumed that only humans have what's called mental time travel. And mental time travel means the ability to travel in the mind's eye to think about the past and plan for the future. And in the Robbie Burns poem, 'To a mouse', Robbie Burns has just ploughed through a field mouse's nest. And he's feeling awful. He's riddled with guilt because he thinks that, thanks to his clumsy actions, the little mouse is not going to make it through the night and it's going to die. And then a thought comes to him and you think, oh, thank goodness for that. And he turns to the mouse and he says, 'still thou art blessed compared with me. The present only touches thee. But oh, I backward cast my eye on prospects' drear. And forwards, though I cannot see, I guess, and fear.' So from Robbie Burns' perspective, said far more eloquently than most of us could possibly dream of, he was thinking that the mouse was stuck in time, that the mouse knew about the present, but had no real notion of the past. It might learn things about the path. That's a good place to be. That's a good place to get food, but not to have an experiential memory of what happened. Nor would it be able to imagine the future and therefore the fact that its nest had been destroyed. If you're just living in the moment that has no significance. I don't need the nest right now. It's not time to use the nest to go to sleep yet. So it doesn't matter. But of course if animals do have a sense of the future, that they really can imagine the future, then that has huge implications. And what we did with the jays was to capitalise on the fact that they naturally hide food. We call it caching just from the French word 'cacher', to hide. But they naturally hide food. And we know that they have excellent memories of where they've hidden their staches or caches of food. And we wondered whether they could also use that information to plan for the future. Because if you think about it, caching by definition is orientated towards the future. The only point of hiding stuff now is if I'm going to be able to get it back in the future, otherwise it's just a pointless activity. And so in the experiment we gave them a series of compartments that they could explore during the day. And each evening they ended up going to bed in one of the two end compartments and it was randomly chosen. So for some that was the left compartment, for some it was the right compartment. But what they learned over six days was that sometimes they'd end up in the left compartment and sometimes they'd end up in the right compartment. And for half the birds when they ended up in the left compartment, when they woke up in the morning, breakfast would be served. Whereas when they ended up in the right hand compartment, when they woke up in the morning. It's like a Motel Six, no breakfast available, sorry guys, you're just going to have to go hungry. And they wouldn't get food until late morning. And for the other half it's the other way round. So it wasn't the location, it's just the idea that you have a sleeping compartment where breakfast will be served in the morning and a sleeping compartment where no breakfast is served, the hungry room if you like. And then on the evening of the sixth day, we gave them the opportunity to hide some food. So we gave them a bowl of nuts and some trays in which they could hide the food. And we found that the birds spontaneously hid the food in the hungry room, the room that doesn't serve breakfast in the morning. Because in the absence of knowing whether you'll be in the breakfast room or the hungry room, then the best thing to do if you like breakfast is to hide food in the hungry room. So you will have breakfast in the morning, bit like taking a packed lunch if you're going on a long hike somewhere.

Chris - Do you think it's just birds that are doing that or would that mouse have realised that it was in trouble because his nest was gone?

Nicky - Well, so far it's only been tested in chimpanzees and corvids. It's not been tested in any other animals. We've done a few experiments in cuttlefish and they're very interesting. They're the cousins of the octopus. And of course they're extremely intelligent, but they're not social. But we've given them various kinds of self-control kind of experiments. So you can have one marshmallow now, well a shrimp for a cuttlefish, or you can have four marshmallows later if you are a child, four shrimp if you're a cuttlefish. And the cuttlefish are able to wait. And we've also shown that if they learn that shrimp are on the menu for dinner, they eat fewer crab for lunchtime. But we've not done these actually carefully controlled future planning experiments yet. But Alex Schnell in my team, along with Elias Garcia-Pelegrin, Christelle Jozet-Alves, and I are just about to start an experiment to see whether the coconut shell carrying octopi are able to plan for tomorrow. But in terms of shelter rather than breakfast.

Chris - It would make sense, wouldn't it, if they could under certain circumstances. The other thing that's often mentioned, when we have young children, we begin to wonder when they realise who they are and what they are. And we do these experiments where we stick things on their forehead and show them their reflection in a mirror. This whole idea of a theory of mind, do your birds have that? Do they recognise themselves? Do they know who they are?

Nicky - Theory of mind refers to the ability to think about what others are thinking and to be aware that your thoughts may be different to theirs. You may know things they don't or they may know things you don't. And it always struck me that theory of mind is rather like mental time travel, except that it's about a different sense of others. So mental time travel is about having an awareness of other times. I know I'm in the present, but I can imagine what I will be doing in an hour's time and I can reminisce about what I was doing an hour before we started our conversation today. So that's all the time. And theory of mind is kind of the same thing, but it's about self rather than time. It's about understanding that other selves can think differently and that my own self can think differently at different times. And so there's a fluidity in that progression, I think. And I think probably the strongest evidence for theory of mind in corvids, and I would say in non-human animals in general, comes from an experiment that we did on the jays, again, capitalising on their ability to cache or hide food. And so what we did is we know that these birds don't only hide their own food, they also steal the food of other birds. And so what we did was we had a setup where the bird either hid food in private on its own or in the presence of another bird who could watch it, couldn't get the food physically at the time because there was a barrier in the way, a window if you like. But the nosy parker could get a good view of where everything was being stashed. And then a short time later, once the potential thief had left the scene, we gave them the opportunity to recover their caches. And when the birds are just cached in private, they recover the food and they eat it. But if others had been watching, then although they recover some of the food and eat it, they move a lot of the caches to new hiding places, which by definition, the nosy parkers that have been watching don't know about because they've now been placed in new hiding places. And specifically probably the most striking finding was it was only those birds who themselves had been thieves in the past that moved the cache to new places, <laugh>. So in short, it takes a thief to know a thief. So birds that have had experience of stealing other bird's caches might be using a form of experience, projection of putting yourself in someone else's shoes and going, 'Hmm, I bet that nosy parker over there might steal my caches. I better move them as soon as they've left to new places because that'll protect them.' Birds that haven't had the experience of having their own caches stolen before don't do it. Suggesting that it's not just a hardwired automatic response that's inborn, but it's actually because of experience. But the birds have never been rewarded or punished for doing this. The experience they've had is of stealing caches, and they're using that experience to predict what another bird might do and then take action in order to protect those caches for the future. So it's a combination of theory of mind, of thinking about what another individual might do, anticipating and predicting what they think it might do, but also integrating that with the knowledge of, I better do this if I want my caches back in the future.

A rook

Nicky Clayton: What we don't know about animal cognition
Nicky Clayton, University of Cambridge

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

Chris - It's been wonderful to chat to you, Nicky, and to see how this has all unfolded over the last about two decades in Cambridge. What do you hope now will be the big questions we're going to get the answers to in your field in the next five years or so? What would you, if you could wave your magic grant wand and also your magic 'let's speed up time, let's do time travel' wand and get the answers to so many things. What are the big questions you want to see solved?

Nicky - Well, I suppose there's various things. One thing is to look in more detail at their experiential memories. The kind of memories that we have when we reminisce about the past. We've already shown that they can remember what happened, where and when, and they can remember who's watching. But two cardinal features of our own experiential memory revolve around the subjective nature of remembering the fact that we often have false memories of things that didn't actually happen to us, but we think they did. So I'd love to know whether they have false memories because it doesn't seem adaptive to have false memories. Surely that would lead to all kinds of inappropriate errors. And yet we think in humans, at least, that the reason we have these false memories is because memory evolved with the future in mind. And therefore it's very good at scenario building. And because the future by definition isn't certain, you want to have lots of different scenarios in your mind so that if things unfold in an unexpected way, you can still partially plan for them. And we think that's probably why we get these false memories, because they're very good at having multiple versions of the same thing, rather than a fixed flat rule about what precisely happened. And then the other one, and it's also related to the subjectivity, is this idea that we remember the source of our experiential memories. So, I know that London is the capital of England, but that's a purely factual memory. It's selfless and timeless. I don't remember how I came to know that London is the capital of England, I just know it. Whereas with an experiential memory, you remember how you know the information. Did I read it on the website? Did I listen to it on the radio? Did I watch it in a movie? I will have access to that information. Did a friend tell me? So I think it would be really interesting to know whether the jays are also able to give us the equivalent of saying, 'yes, I saw it or I heard it,' or for a cuttlefish it's, 'I saw it or I smelled it'. So I think there are two kinds of things about experiential memory that would be really fascinating to know more about. So that's one big question I think. I suppose the other one is thinking in more detail about whether we will ever be able to make some inroads into whether or not animals other than human beings are conscious. Obviously when you're talking about phenomenology, like are you aware of what you just saw? Are you aware of who said what to you? When are you aware of your memories? Are you aware of your plans for the future in humans? This is all couched in terms of linguistic things. We talk to one another in terms of sharing our memories and our stories and our plans for the future. It's not clear how one can do that in any animal, including the corvid in the absence of any agreed non-linguistic markers of consciousness. But might we be able to get somewhere through these other roots, through these things like asking questions about whether they know whether they saw it or heard it? Do they have false memories? Are they more confident in some memories and not others? And I think that would make a real inroad to discoveries if we could establish that through behavioural criteria on a firmer footing and have enormous implications for things like animal welfare.


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