Neuroscientist Onur Güntürkün on the ability of self-recognition, the mirror test and why pigeons are frightened of their own reflection

videos | March 19, 2020

Possibly every morning, when you wake up, you go to the bathroom, and then you look at yourself in the mirror. This is what I do and what possibly you do. You don’t even think that it is another person looking at you; it is absolutely clear that it is you that you see in the mirror, not another person. But when you were one year old, and you were looking like a young baby in the mirror, you did not know that it is you: this comes later during our development (as far as we understand, with about one and a half years and maybe even a bit later) that it’s us who is in the mirror, not another person. Very young children look into the mirror and say ‘Hi!’ or turn to their parents saying ‘Baby, baby, baby!’ So they think that it’s another person.

If you test your cat or dog, these cats and dogs and many other animals won’t recognize themselves in the mirror. They think it’s another animal, but that’s the animal that is always there. I do not know what your cat thinks, but possibly what your cat thinks is, ‘There is always this cat in the living room! And I don’t know where this cat belongs to, but always when I’m going to the living room, there is this cat!’ So cats, dogs, and most other animals don’t recognize themselves in the mirror, but some animals do: as I told you, it’s humans, but also a few other animals like, for example, chimpanzees.

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How do we know the chimpanzees recognize themselves in the mirror? There is a very simple test, and you may have heard about it. When you give a chimpanzee a mirror for the first time, the chimpanzee becomes anxious: it looks at the mirror, tries to look behind the mirror, moves its head and tries to see if there’s a correlation between its movements and the movements of the animal in the mirror. After a while, it calms down and makes faces as we do in front of the mirror. But the real test is when you put a little dot on the forehead of the chimpanzee: when it looks into the mirror, it starts scratching it on its forehead. So it doesn’t try to scratch the surface of the mirror trying to get the dot off the forehead of the other chimpanzee: it touches its own forehead. This is a classic test to know if the chimpanzees recognize themselves.

Are there any other animals that also do this? Yes.

Orangutans can recognize themselves in the mirror, possibly Asian elephants can do this although the results are not very clear. There is a very recent report that even some fish can do this, magpies can do this, and there was an old report that dolphins can do this.

But I did not think, together with my colleagues, that this dolphin paper was a good one. So we tested dolphins. But how do you test dolphins? You make the chimpanzee test by putting a dot on the forehead, and the animal has to scratch it, but you need your hands to do this. Dolphins have no hands. How do you test them? And we came up with a good idea, or I think at least it was a good idea.

But first I have to tell you what you have to do with the dolphins on sunny days in the dolphinariums nearly every day. When you go to a very warm country, and you’re at the beach, you possibly put cream with sun blockers on you. You have to do the very same with the dolphins: under natural conditions, they dive deep into the water where the sun can’t reach, but in the dolphinariums, they’re always at the surface of the water, and they can get sunburns. So you have to train the dolphins so that they come to the edge of the pool, and then you take the sun blockers and cream the animals with them. The animals do this nearly every day.

We created a yellow sun blocker, so we had two pots: one with the usual sun blocker and the other one with the yellow sun blocker. So the animals were coming to the edge, and we were putting on the sunblockers. Then, without the animal being able to see it, we took the yellow sunblocker and made a mark around the eye. Then we gave the animals mirrors, and what we saw was that they were turning their heads to get a better look at the mark. That’s interesting! We took another dolphin and put a mark around its eye. We wanted to know if an observing dolphin also does this when it’s seeing the other animal so that it may mimic the movements of the other animal. No, it did not care. So, it seems that dolphins recognize themselves in the mirror. And then we observed something that was not planned, but that was fantastic: the animals swam to the water’s surface, and they tried to catch their reflection on the water’s surface because the water surface is a bit reflective, they can see this yellow mark at the water surface.

So this is a fine story, but it doesn’t explain why some animals recognize themselves in the mirror and other animals don’t. Is it really so that only a handful of animals recognize themselves in the mirror? I don’t believe that. I believe that there are three groups of animals on this planet.

Some animals really don’t recognize anything and they think it’s another animal. Some animals like chimpanzees and humans recognize themselves in the mirror. But there is a large group in between: they know that this is not another animal but they don’t understand that it’s them.

How do we test this? We made an experiment (just as an example) with pigeons. We took pigeons and gave them a cup of food, so they rushed there to get the food. Behind the cup, there is a glass, and behind that glass, there is a second cup of food, and from that direction, another pigeon is rushing towards this second cup of food. When I’m observing the pigeons, they just go to the cups and eat; they don’t care about the other animals. Now, I don’t put glass between them, but I put a mirror, and what the animal sees is a pigeon rushing to the food, so it sees itself. It’s practically identical: a pigeon coming to eat that food. But this time, the animal stares at the mirror; it’s frightened, and it comes very slowly closer. It’s eating, but it’s always looking into the mirror in panic. But when you do the mark test, pigeons don’t pass it. Pigeons seem to understand that this is not another pigeon, but it’s a strange pigeon: it does the same that I do, but it’s not me.

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The interesting thing is, how do pigeons and other animals understand that this is a strange pigeon, a strange hen, a strange monkey? How do they know that this is something very strange? In the beginning, I told you that the chimpanzees, when looking into the mirror for the first time, were panicking. Then, they were looking for the correlation between the movement of the other animals and their own movement. This is how children discover that it’s them in the mirror. When they reach the age of about one and a half years or slightly older, they stand again in front of the mirror, and they suddenly realize when they do something, the other boy is also doing the same thing. This is how they understand the correlation; this is how they understand that it has to be me. But now, think that you can detect the correlation, but you do not have the intelligence to conclude that it is you: then you are in the middle, where most of the animals are. This is a strange animal: it does everything I do, but I’m not intelligent enough to understand that it’s me.

Under some neuropsychological conditions, after lesions of the right hemisphere, some humans lose the ability to recognize themselves in the mirror. They say that there is always this man in the wheelchair who shows up in the bathroom; he always wears the same shirt that I am wearing, and he’s a very strange guy. He is harmless, but I don’t know why he is always in my bathroom. They lose the ability to recognize themselves, but they’ve never lost the ability to recognize the correlation and the similarity: they are drawn back to the stage of many animals that recognize the correlation but are not able to recognize that it’s themselves.

So next time you go to the bathroom, and you look into the mirror, think of all of the other creatures on this planet that do the same as you do without understanding that it’s themselves looking into the mirror. Still, they detect the correlation, and they’re frightened of the other animal.

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Professor for Biopsychology at the Institute of Cognitive Neuroscience, Ruhr-Universität Bochum
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