#205 – The most insane things fish can do (Sébastien Moro on The 80,000 Hours Podcast)

We just published an interview: Sébastien Moro on the most insane things fish can do. Listen on Spotify or click through for other audio options, the transcript, and related links. Below are the episode summary and some key excerpts.

Episode summary

In today’s episode, host Luisa Rodriguez speaks to science writer and video blogger Sébastien Moro about the latest research on fish consciousness, intelligence, and potential sentience.

They cover:

• The insane capabilities of fish in tests of memory, learning, and problem-solving.
• Examples of fish that can beat primates on cognitive tests and recognise individual human faces.
• Fishes’ social lives, including pair bonding, “personalities,” cooperation, and cultural transmission.
• Whether fish can experience emotions, and how this is even studied.
• The wild evolutionary innovations of fish, who adapted to thrive in diverse environments from mangroves to the deep sea.
• How some fish have sensory capabilities we can’t even really fathom — like “seeing” electrical fields and colours we can’t perceive.
• Ethical issues raised by evidence that fish may be conscious and experience suffering.
• And plenty more.

Producer: Keiran Harris
Audio engineering: Ben Cordell, Milo McGuire, Simon Monsour, and Dominic Armstrong
Content editing: Luisa Rodriguez, Katy Moore, and Keiran Harris
Transcriptions: Katy Moore

Highlights

The ingenious innovations of Atlantic cod

Sébastien Moro: If there was one study that blew my mind, it’s the one I’m going to explain now. It’s a paper on Atlantic cod. At first this study was about self-feeders for aquaculture. So in aquaculture it happens that the fish have self-feeders: some kind of devices they activate themselves to get food. If I remember correctly, they were trying to find food preferences in these fish.

So first, they need to recognise each fish. So they put a tag on their back with a bead on it, a coloured bead. So you have the fish with the blue bead, the one with the red bead. And then inside the tank you have a self-feeder. How does it work? Let’s imagine again a square tank seen from top. On the top left, you have the device. The device is a pull string with another kind of bead at the bottom. The idea is that the fish comes, takes the bead in its mouth, pulls, and then there is a light that switches on top of the device and the self-feeder is releasing food on the top right — which is kind of problematic, because it means that the fish that pulls is not the first one where the food is.

Luisa Rodriguez: Right. Because it’s on the other side of the tank.

Sébastien Moro: Exactly. So they were trying that, and it was working pretty good.

And then, it happened with three fish, but I will concentrate on one. There is one fish who got trapped in the bead of the pull string with his own bead, the one in his back. There is a video of it. So you can see the animal getting locked in it. It starts to get scared, tries to move, but can’t. But the device is working: the fish is pulling, so the light goes on, the food is given and the other fish are going to eat. And finally, this fish managed to unlock himself and move.

Then the weird thing is scientists started to see this fish trying on purpose to get stuck in the bead again. And they were like, “What the fuck is this animal doing?” And the fish started to be really good at it. And at the end of the experiments, the numbers are something like the animal used his or her mouth 40 times, and the bead 522 times. Why? Because when you pull with a bead in your back, you can have the head where the food is coming.

Luisa Rodriguez: I see.

Sébastien Moro: And what they observed is that each of the three fish who did that learned a different technique, and they improved it. When you watch the 10 first tries, they’re just trying in kind of an easy way to get locked in it and then free themselves to go to the food. But the 10 last tries, it’s amazing, really: the animal is going down, grabbing the pull string with their own bead, pulling while turning, which allows them to free themselves. And when the device is activated they are already free and they head at the food. Which means they are using an artificial limb that is in their back that they cannot see to overcome a difficulty.

It’s something that was not expected by the scientists. At no point did they think they would see that. They’ve been publishing a paper just on this, aside from the one they were preparing, because it was insane. And it’s Doctor Octopus. Like they have one more arm. One arm.

Luisa Rodriguez: Yeah. So they basically just made up a new way to make sure that they’re quicker to get to the food as it comes out. And then they experimented, improved upon it, and now it’s like the Olympic games of using their extra tool appendage bead on their back to be quick to the food. That’s absolutely incredible. It’s tool use, but it’s also so flexible. I mean, I can’t think of anything in the environment that would make you think that they have any kind of related skills, or inherited behavioural techniques.

Sébastien Moro: Yeah, this is really, really something. Honestly, the first time I read that I was like, okay, I’m going to read it again. I misunderstood and I didn’t. And nobody ever talks about this paper. Every time you can see stuff about how fish are smart, this one is never in it and it’s an amazing paper.

The mirror test triumph of cleaner wrasses

Sébastien Moro: The idea is you put a subject in front of a mirror, and then if the individual can recognise himself or herself, he will go through different stages.

The first stage is you don’t know it’s you, so you consider that it’s someone else. But you should start to see some social behaviour.

And after a little while, the subject will start to understand that there’s something going wrong there, something’s not right. So you should start to see weird behaviours that aren’t used in the social context, like moving your hand to see if the other one is doing the same thing.

Then the next stage is the subject understands that it’s his reflection, so you should start to see self-checking behaviour. […]

And the last part, to officially validate the success of the mark test, you put the subject to sleep and draw a mark where they cannot see. […] And then when the subject wakes up and looks in the mirror, either it doesn’t care, or it’s starting to try to remove the mark on him — so it means that the subject understands that it’s his reflection and he can orient the movement toward himself or herself.

So they released last year, very recently, the most amazing test ever, that hasn’t been done on any other animal. They’ve made a photographic version of the mirror test, so nobody could say it’s scratching. It can’t, because the fish has no mark.

First they made them pass the mirror test, all the stages and everything. But this was the training. So now this test is just a training for them. Then the test was that you take a picture of this very fish and you draw a mark on him or her, or you take a picture of another cleaner wrasse with a mark. The animal tries to rub himself or herself only when it’s a picture of him or her. That’s not all. I have worse.

Luisa Rodriguez: Wait, wait. I just want to make sure I understand that. So you take a picture of the cleaner wrasse and you draw a mark on them. And if they try to rub the mark off, that’s already pointing at something like […] there’s just like nothing physically there that would make them, for physical reasons, want to rub it off — except for the fact that they think that they see it in a reflection of them.

But it’s not just that: they only do it for the pictures that are recognisably of them, which is incredible. I guess that means that when they were doing the original training for the mirror test, they saw themselves in the mirror, and they learned what they looked like, and they learned to differentiate that from what other cleaner wrasses looked like?

Sébastien Moro: Yes, you’re understanding right. There is a second part to this test. We wanted to know if the fish are recognising themselves by the face (as we do in humans), or by the body, or a combination of both. We know, for example, that humans are using the face primarily.

So what they did is they took Photoshop, they took two pictures of fish — one of the focal animal and one of another one — and they cut the heads on the pictures, and put the head of the focal fish on the body of another one and the head of the other one on their body. And they’ve tried it again, and it appears that they’re attacking their body with the head of someone else, but they’re not attacking a picture of their face on someone else’s body. So it means that they can recognise themselves in pictures from the face, exactly as humans do. This is the best mirror test ever. Actually, the animal that is succeeding at it the most convincingly, except for humans, is a cleaner wrasse.

The astounding accuracy of archerfish

Sébastien Moro: So to explain briefly: what are archerfish? They’re called Toxotes, scientific name, and they are hunting fish. They eat mostly insects, and when they’re young, they eat prey in the water, as every fish. But as they grow, they start to spit water spray out of the water. They spit, literally, to hit insects which are on the leaves of the plants above the water.

But this is not something that is instinctive. They have to learn it. At first they’re bad, and then they’re better and more impressive: they slowly learn to hit moving prey. And they can hit moving prey, they can learn that just by watching other fish doing it, without even trying it themselves: once you release them, they’re able to do it.

Now, this seems impressive, but it’s not as much as it is really — because we have to remember that these fish, they’re not territorial; they move all the time, which means that they don’t know the place, so they really use their sight to hunt. Then when you are in the water, when you’re comparing to the air, there is a refraction index that changes. So where they see the insect is not where the insect is — exactly how when you put your arm in the water, it looks like your arm is broken, but it’s not, it’s refraction indexed.

And they can just correct for the refraction index, knowing that this refraction index will change according to the pressure, to many things. And they can adapt it to the height of the prey, the speed of the prey, if there is wind or no wind — which they can’t feel, because they are in the water — and they can shoot a prey and calculate where the prey will fall to be exactly at the landing spot of the prey, to be the first one to eat.

Their visual cognition is so good that they can even recognise human faces — which is totally insane, because in their life they shouldn’t be recognising them.

And even more impressive, they’ve shown that they can recognise faces of humans with rotations. So they learn to recognise the face of someone, and when you put this face next to 44 different faces, they can still recognise this one. But if you learn one face, and then I show you a profile of this person, it’s much harder to recognise this person. Monkeys, primates have a hard time doing it. The archerfish can do it. It’s insane.

Their vision and their ability to understand visual stuff is crazy. Like, really crazy. So here we cannot say that water is not tool use. They are using water as a tool. And they even watched in detail how the jet is made, and they found out that they change the shape of their mouth when they’re spitting — so the end of the spit is bigger or smaller, the track behind is longer or not, just to be precise on the distance. So they’re really very precise on how to spit. It’s ballistic. It’s absolutely ballistic.

Luisa Rodriguez: Because it’s through water, you’ve got the refraction, you’re using water sprays that you create with your mouth. It’s just actually unbelievable.

The magnificent memory of gobies

Sébastien Moro: There is a very interesting and funny story. It’s one of the first papers we have on fish. It was in the ’50s and ’70s, so it’s really old. And one guy noticed that gobies, these fish are first living at high tide, and they’re checking the topography of the floor of the sea. Then the tide is going away, and they’re choosing a pool to be their home pool. And when the tide is away, they’re living in a small pool.

And the guy working on that, Lester Aronson, discovered that these fish were sometimes jumping from one pool to the other. But the problem is, when you’re inside the pool, you don’t see the other pool. But the fish were insanely accurate. So the question was, can they somehow fly, so they jump to the spot where the next pool is and they’re flying there? Or do they remember?

So he first checked what they were doing, and it seemed they were scanning at high tide, memorising the full area, and then jumping from memory. And he proved it. How did he do it? First, he took the fish from the home pool and brought them somewhere else, with different pools that these fish had never seen before. The fish were not jumping anymore. And when they were jumping, they were falling on the stones around on the rocks. They were missing pools all the time. So that was the first interesting thing.

And then a few days or even weeks later, he brought them back, and they still remembered. So they had a topographical map in their mind that they saw from top, at first in high tide, and then from inside and subjective view. And they could still jump precisely.

And there have been many tests on these fish, even a recent one, that showed that they can remember the area for at least a month and probably more. And they can go back to the sea.

Luisa Rodriguez: That’s insane! So it’s something like there are hills and low points in the sand, or whatever the bottom of this area is, such that when the tide goes down, some of the low points still have water in them, and those are the pools. And while the water is still high, not only are they able to work out that the deep bits are going to be the pools, but they also create a map — and they create a map with enough accuracy to, while in one pool, know that if they go like 36 degrees to the left, they will be in another pool. Jumping pool to pool. I mean, I feel like I’m like, “But do they remember things for more than three seconds?” And you’re like, “They actually remember better topography than humans do.” There’s no chance I would do that. That’s amazing.

The tactical teamwork of the grouper and moray eel

Sébastien Moro: Now I’m going to something even more incredible, which has been studied in depth: the grouper and moray eel interspecific hunting. So what is a grouper? A grouper is a carnivorous fish, which is massive. It can grow up to two metres long. It’s a really massive fish. It’s a Formula 1 fish. It swims very fast, it’s very big, it’s very powerful. It has a massive bite force. And it’s a diurnal hunter, so it hunts only during daytime.

Now we have the moray eel. Moray eels have very snaky-shaped bodies. They are nocturnal hunters. They don’t hunt during daylight, and they are more made to go inside crevices, inside holes and this kind of thing.

So two very different hunters. The groupers, when they are hunting a prey, it often happens that the prey is hiding inside the coral reef. And at this point, the grouper can’t get inside. Well, the grouper developed a communication with the moray eel with a kind of head shaking. We have lots of videos of it. It goes to find a moray eel and shakes its head above the moray eel to ask the moray eel to come and hunt with him. Sometimes the moray eel will accept. Sometimes it won’t, because it’s sleeping.

So let’s say it’s coming. If the moray eel finds another hole, it might go inside and sleep. So the grouper will come back and go like, “Oh, we’re going to hunt.” And then the grouper is going exactly where the prey entered inside the reef, and the grouper will point at the hole. This is one of the only referential gestures we know in animals, because it means that the fish is not communicating just a feeling, an emotion or something like that: pointing at something external from him and saying to the moray eel, “You have to get here.” And the moray eel understands it and gets inside.

You can find videos everywhere on YouTube about that. This is quite amazing, because almost everything is directed by the grouper. Then the moray eel gets inside, and the grouper is waiting outside of the reef. And there is no sharing of the prey: it’s either the moray eel gets the prey, or the prey escapes from the reef and she has a massive Formula 1 killer waiting for it. And so either the grouper wins, either the moray eel wins, and then they continue hunting like that so each one has their meal.

And they found out that groupers can hunt with pretty much any animal that will accept to hunt with it. We have videos of some species of grouper hunting with octopi. We are now talking about a vertebrate hunting with an invertebrate together and communicating. This is something we don’t have on land that easy.

And one interesting thing is, when they don’t know very well the environment, and don’t really find someone to help them, they will just point until someone finds and helps them. And sometimes, they have been observed pointing for up to 30 minutes.

It’s really impressive. Sometimes it’s fish: there are fish with very strong jaws and they can bite inside the coral reef, so sometimes they’re hunting with these fish. It depends a lot.

The remarkable relationships of wild guppies

Luisa Rodriguez: OK, so social learning sounds at least present for some species. Do fish have recognisable relationships between each other? Do they seem to form bonds? What else are their social lives like?

Sébastien Moro: Oh, I love this question. Do we know if they form bonds? There have been many species tested for that, especially guppies. We have discovered social networks in guppies.

There is one paper on wild guppies where they really built a social network. They took every animal from two ponds that are linked by some water flow. They found out there were three communities of fish always interacting together. And between those communities, there were animals doing a link between the communities; they were always switching from one to the other. You have central animals with lots of relations with lots of other animals, you have more peripheral animals, you have a lot of different kind of animals — because they have personalities, as every animal does, so it changes depending on the personality.

And in guppies, the bond doesn’t seem to be in how long the animal spends next to another one, which is usually what we use to know there is a bond, but it’s more about the frequency. They are often found one close to the other, but not for a long length of time. When, if you’re talking about cows, for example, when they have a friend, they stay with a friend all the time for years.

So we have that on guppies, and we have other fish that have stronger bonds. One very interesting one was a study about prosocial behaviour. So the idea was to take fish who are bonding for life, male and female, a bit the same kind of animal as the one I talked about in the judgement bias study. And they took the male out, and they split the male and the female.

I’m explaining this, so try to visualise this in your head. You have a tank split in two parts: the part closer to us, there will be the male; in the other one, there will be different people. In the part of the male, you have two compartments: one compartment with a red [circle], the other compartment has a blue triangle. So if the fish gets in the compartment with a red circle, it will receive food, and food will be delivered in the other tank as well. If the fish takes the blue triangle, this fish will receive food, but nothing will be delivered in the other tank. So we have a prosocial choice and antisocial choice.

So when there is no one in the other part of the tank, the male is choosing randomly. If there is a male, a possible rival: antisocial — almost 100% of the time, antisocial. Now, if there is his wife — yes, this is anthropomorphising; I don’t care — there is his female, this is a prosocial choice all the time.

And now a question: what happens if you put in a new female? Is it just because this is a female or is it just for their female? Well, if their female is just next, when they’re bringing a new female, it’s the antisocial choice all the time. Now, if there is not the female of the male, it will depend on how long he’s been separated from his female. At first it will be antisocial, and after a while he will start to switch to prosocial choices.

Luisa Rodriguez: Oh my goodness. OK, so if his female is just like in the vicinity, he’ll be antisocial around the other female. But if she’s gone, and she’s gone for a while, he’ll start to become prosocial with this other female. Oh, that’s complex.

Sébastien's take on fish consciousness

Luisa Rodriguez: From your perspective, you know so much of what there is to know about fish that we have studied so far, so you’ve got all of this wealth of knowledge: what is it that feels most compelling to you, that makes you feel like you’ve got really high confidence that fish are experiencing things?

Sébastien Moro: Most of the papers we have are going in this way, and very few — very, very few — are going the other way.

So what makes me so certain? I’m really talking about my personal opinion here. I tend to think that emotions… What are emotions? What are emotions used for? They are putting a gloss on what is around us: “This stuff has a positive gloss; I need more of this. This one has a negative gloss.” And we know that emotions are very, very closely linked to learning. So emotions are something that attract or repel. And it seems pretty obvious that it must have appeared very, very early in evolution, because this is how we work.

This is maybe one of the biggest differences with algorithms. Algorithms are following closed loops. And this comes up when animals are more driven by emotions, by value of things, which is made by a kind of limbic system that says, “This is good, this is bad. You want more of this, you want less of that.” And I don’t understand why other animals couldn’t have had that.

And another thing is, I’m reading a lot about bees, so I know very well the corpus of knowledge on bees at the moment. And we’re starting to have the same results in bees. So I’m not 100% certain now that bees could be sentient, but the biggest leader of bees research today, Lars Chittka, has said on Twitter that bees are sentient for him. And the results we have are going in this way. So they have a one-million-neuron brain, and the brains of fish are much, much bigger. And when we split from insects, brains were not existing either. So it’s just a convergent evolution.

Fish have complicated lives; they have social lives, very social lives. I guess we’ll talk a bit more about this later, but I already introduced this with cleaner wrasses: their lives are very complicated. They have challenges that they have to overcome that are as complex as what we find in mammals and birds, maybe more sometimes. So them having no sentience, when we recognise sentience in birds and mammals? It’s either you refuse it for everyone, or you accept it for everyone at the moment. Not for everyone, because animals with a brain or central nervous system, today we think at least there should be a kind of global network; everything should be put in common to make a unified vision of you and this kind of thing.

But consciousness probably has many degrees; sentience has pretty much many degrees — but not degrees on a ladder, degrees more on a circle. But that would sound just weird actually, that they wouldn’t be sentient.