>> The content of this issue is adapted from the "unread" popular science book "Fish Know Everything", written by Jonathan Balcomb, a well-known American animal behaviorist, and the broadcast of this program has been authorized by "Unread", and I would like to express my gratitude.
In today's issue, we're going to explore whether fish also have consciousness and thought. To illustrate this question, let's start with a basic question, that is, do fish feel pain?
Here, we need to distinguish between the physiological response to pain and the difference between pain perception. Some animals act of avoidance even when they do not feel pain, which is a simple conditioned reflex, a physical movement caused by nerve and muscle activity, without conscious participation. Deep vegetative people who have completely lost consciousness on people will also have some basic physical reactions, such as shaking their hands and turning their eyes, but they are actually unconscious and do not feel pain.
There is no doubt that fish will react physiologically to pain, and if you poke the fish in the tank with a stick, it will definitely escape. But do fish have a sense of pain? Some people believe that since the fish is a vertebrate, the structure of the body is the same as that of mammals, and one of the most crucial points is that it has a peripheral nervous system controlled by the brain. For fish, detecting dangers around them, remembering the injuries they have suffered through pain, and thus avoiding these injuries is consistent with evolutionary theory.
But Professor Ross of Pennsylvania State University in the United States believes that this is all human assumptions. He published a paper titled "Can Fish Really Feel Pain?" ”。 He threw out his own view in the paper that fish are unconscious, that is, fish do not perceive anything, have no feelings, do not think, and cannot even see things. Pain, he says, is a conscious experience, so of course it's impossible for a fish to feel pain.
Ross argues that a theory called "cortical centrism" supports his view. The theory is that if an animal has the same ability to feel pain as a human, the animal must have a neocortex, a part of the brain that has grooves and loops like broccoli. The word neocortex means "neocortex" in Latin. The neocortex is "new" because this layer of gray matter is the most recently evolved part of the vertebrate brain, which is only found in mammalian brains.
But there is a clear counterexample to this theory, and that is birds. Birds do not have a neocortex, but birds are generally thought to be conscious because they have many cognitive skills, such as making tools (such as magpies nesting with branches), recognizing the way according to the characteristics of the location, and making a call at dusk to call the young birds back to the nest.
But there is also good evidence for the idea that fish are painless and unconscious, with fish biologist Jones writing in a book for sea bass anglers that sea bass that are caught and then released return to the same place to bite hooks that day or the next day, sometimes more than once. Doesn't this mean that the fish are not aware of the pain? However, Jones's claim has not been confirmed by research.
Instead, one study showed that fish, if caught by hooks and fishing lines, take a long time to return to normal activity. The carp is hooked once and the second bite is three years later. A series of experiments on largemouth bass have also shown that the fish can quickly learn to avoid fish hooks and can persist for half a year without being deceived.
As for why some fish are repeatedly hooked, Karem Brown, who studies fish cognition and behavior, said that it is purely because they need to eat! For fish, the uncertainty of life is too great, and it is really possible to be starved alive, so they will never miss any opportunity to eat. Many fish will continue to bite the hook even when they are full. Brown said, just imagine, if you are hungry to the chest and back, and you may have to hang up without eating, someone keeps stuffing fish hooks into your burger, and one of the ten burgers will make you bloody, then you can only take risks in order not to starve to death.
Nord Greene of the Norwegian Veterinary College and Garner of Stanford University used experimental methods to study the pain of goldfish. They fixed small heaters made of aluminum foil to the bodies of 16 goldfish and slowly heated them up. Half of the goldfish were injected with morphine, and the other half were injected with only normal saline. The researchers believe that if the goldfish can feel pain, then the goldfish injected with morphine can withstand higher temperatures before responding.
However, the results of the experiment are different from what the researchers thought. Both groups of goldfish exhibited normal pain responses. They begin to writhe, and the temperature they feel when they react is the same. But when they were put back in the tank for half an hour and then observed, the two groups of fish exhibited different behaviors. Goldfish injected with morphine swim around normally, while goldfish injected with saline have more escape reactions.
Photo by zhengtao tang on Unsplash
This study shows that fish can feel both the initial sharp pain caused by the injury stimulus and the persistent pain that follows. This reaction is like our hand touching a hot stove, and at first the reflex, the hand is pulled back, the brain is basically blank, and it will take about a second for us to really feel the impact of the pain. After that, we will eat a long and wise, and the pain will make us avoid making fools again.
It is worth mentioning that the experimental device just mentioned is equipped with a temperature sensor and a safety switch, and researchers can turn off the heater in time without causing burns to the goldfish.
There are already a number of veterinary institutions that support the idea that fish have pain. In 2012, a group of leading scientists gathered at Cambridge University to discuss the scientific community's understanding of animal consciousness at the time. After a day of discussion, they jointly drafted and signed the Declaration of Consciousness, which was a clear refutation of cortical centrism. The declaration mentions that in the course of biological evolution, the neural circuits that dominate the behavior and electrophysiological responses of attention, sleep, and decision-making have existed as early as insects and cephalopod molluscs (such as octopuses) in the invertebrate stage; it cannot be judged that an animal does not experience an emotional state just because it does not have a neocortex.
The american veterinarians association is the american veterinarians who has made it more explicit to express its views on the problem of fish pain. It mentions in its 2013 Animal Euthanasia Guidelines that experiments have shown that when fish are stimulated by injuries, the forebrain and midbrain produce significant electrical activity, which overturns the idea that fish's response to pain stimuli is only a conditioned reflex; the available evidence shows that fish, like terrestrial vertebrates, try to avoid suffering from pain.
Did these conclusions put an end to the fish's pain and consciousness struggle? Not really. It has been suggested that the scientists' study only proves that a few fish have pain, and does not mean that most fish also have pain awareness.
You can't say there's something wrong with this kind of questioning, and the part really can't replace the whole. But if we're going to think about which is more likely, like if you have to go into a gamble and you have to make a choice or you're going to be unlucky, I think most people will still choose a conclusion that has at least some evidence.
Scientific research is often about constantly adding credibility to a proposition, and it is likely that we will never reach 100% credibility, such as in the field of high-energy physics, which is about the concept of confidence. Now that it has been proved that some fish are pain conscious, this adds credibility to the proposition that most fish are pain conscious. Therefore, on many issues, scientific thinking makes us consider probability problems, not right and wrong questions. This kind of thinking makes us quite useful in dealing with the various choices in daily life, and rational choice is to take the side of the higher probability, even if you know that it is not 100% correct, but it is the best choice.
Let's talk about another more important topic, do fish have ideas?
Over time, evolution has mastered animals for the things that matter most to them. Fast action is paramount to certain animals, so chimpanzees are good at climbing, cheetahs run fast, and kangaroos jump invincible. And if Phelps and Sailfish were to compete, Phelps had not had time to breathe, and the sailfish had swum 100 meters away. Physiologically, the mechanism of natural selection will make the genes more suitable for survival continue to be passed on, and mentally, it is actually the transmission of merit.
Nature has set puzzles for people and other animals. If solving this problem will bring a huge survival advantage, then after a period of time, long or short, the organism will have the cognitive ability to understand the problem. Modern cognitive ecology holds that intelligence is shaped by the various survival needs that animals face in their daily lives. So, some birds can remember tens of thousands of places where they buried their fruits, rodents that burrow can understand the underground labyrinth in two days, and crocodiles can calmly carry branches to the bottom of the heron's nest and swoop down to collect building materials.
Do you think the fish look a little inferior to the skills of these animals? In fact, the fish are very smart, they not only forage, but also avoid danger, the way is to jump the dragon gate.
The example of the deep goby may illustrate the intelligence level of the fish. This is a species of fish that lives in the intertidal zone on the east and west coasts of the Atlantic Ocean. At low tide, goby deep goby prefer to stay close to the coast, hiding in a lonely warm puddle of water, where there is plenty of delicious food. However, there are pros and cons, and when they come out to feed, they may encounter octopus or herons, at this time, they have to desperately escape. If you slow down, it becomes someone else's meal. But where can a small fish hide? Don't you say, it's smart enough, it's going to jump into the puddle next to it. And one jump at a time, they will not jump to the rocks and be sunburned alive. Some people have analyzed that deep goby can swim at full tide while remembering the terrain in the intertidal zone. The distribution of low-lying geology, they are ripe for the heart, because these places will form puddles after low tide.
Pictured: Deep goby
The late Leicester Aronson, a biologist at the American Museum of Natural History, proved that goby have the ability to recognize the way. He made an artificial reef in his lab. He then prepared a stick to poke the puddles, which would make the fish think that a predator was coming, and the fish would jump. If a fish has the opportunity to swim around the lab's artificial full tide, it has a 97% chance of jumping into a safe puddle. The ignorant little fish who have not experienced the full tide have a success rate of only 15%, and it makes no difference to jump around with the stool. Aronson's theory is that after a full-tide learning period, the goby can remember the escape route in 40 days.
The example of the deep goby not only shows that the fish will create their own ways to avoid danger, but also shows that the fish's memory is very good, saying that the fish's memory can only rest for 7 seconds. So, how long can a fish's memory be? Tony Puncher, a biology professor at the University of British Columbia, did a classroom study many years ago while teaching animal behavior.
At the time, students were studying the color vision of goldfish. Each fish has a feeding tube with a slight difference in color, and experiments have proved that goldfish have good color vision. After the experiment, the goldfish were put back into the aquarium. Originally, this was the end of the matter. Coincidentally, the following year, some of these goldfish mixed with other goldfish who had not participated in the experiment and participated in the same experiment. When these old contestants were placed in an experimental environment, they would quickly point to the previous tubes to find food, apparently remembering the details of last year's experiments, including the exact color and location of the tubes.
The reason why many people think that the fish has only 7 seconds of memory stems from a widely circulated chicken soup for the soul a few years ago, it is said that the fish has only 7 seconds of memory, and after 7 seconds it will not remember what it has been, and everything will become a new beginning; therefore, the fish will always be excited, never bored; sometimes, we should be like the fish, learn to forget everything.
In fact, the point he finally said cannot be said to be completely wrong, forgetting pain is indeed a self-protection mechanism for people. But I have always insisted that the expression of any point of view cannot be based on false facts, even if the final conclusion is correct, if the argument is fictional, it is not a good argument. In the same way, using lies to combat rumors is also something I am very opposed to. In the face of controversial topics such as genetically modified organisms and traditional Chinese medicine, we must not use lies to combat rumors.
Humans have long considered themselves to be the only species that can use tools. Later, in the middle of the last century, Jenny Goodall discovered in Africa that chimpanzees would poke ant holes with dry branches to catch ants to eat, breaking the sense of superiority of humans. The discoverer of the tools that fish also use was Bernardi, a professor of evolutionary biology at the University of California, Santa Cruz. He was the first scientist to photograph fish using tools in 2011. In this video, we can see a saddle-spotted pigtooth fish carrying the clam to the bottom of a large rock, and then smashing the shell on the rock with its mouth, smashing it several times, and finally succeeding, you can eat the clam inside. Note that when the pigtooth fish was halfway up, it stopped to try to see if another smaller rock on the sand was good. It casually tried to throw it a few times, then continued on its way, as if it felt that the stone was not worth wasting its own time. This is a test of the tool, which definitely contains the thinking process of the fish.
Even if this particular pigtooth fish is as rare as Hawking, its behavior is still worthy of our admiration. However, some stubborn skeptics have suggested that this behavior is not really the use of tools, because it does not use one object to control another, unlike when we use an axe to split wood or a chimpanzee to grab termites with branches.
Just as the pigtooth fish use water to wash away the sand, the water fish also use the water to feed. The waterfish is a fish about 10 cm long that lives in tropical waters, with a silvery body and a row of beautiful dark spots on the sides. They are mainly found in estuaries, mangroves and streams. They can press their tongue against the groove in the upper jaw and then suddenly contract their throat and mouth, which can quickly spray up to 3 meters of water column. Shooting fish will ambush in the backwater under the leaves inhabited by beetles or grasshoppers, spraying water from 1 meter away, and some fish have a hit rate of almost 100%.
Pictured: Shooting water fish
Why can it be a hundred shots? High-speed video recordings show that water-shooting fish adopt different strategies depending on the speed and location of their flying prey. Specifically, it is to adjust the trajectory of the water spray according to the flight speed of the insect. If the insect flies fast, the water fish will aim in front of the insect. If targets fly low, usually less than 18 centimeters above the surface of the water, they adopt a "turn and fire" strategy. That is, the body rotates horizontally to match the lateral trajectory of the target prey, so that the jet water flow can "track" the target's movement path in the air. This technique is probably admired even by the rugby quarterback.
There's a saying you can listen to and decide for yourself whether to believe it or not. Shooting fish can adjust the shooting according to the visual dislocation caused by the refraction of light at the interface between water and air, and judge the size of the prey and the relative position of itself and the prey. Once they have summarized the rules, they can judge the actual size of their prey from unfamiliar angles and distances.
Even more powerful than the shooting fish is a fish called the dog fat carp. The carp lives in the freshwater waters of Africa and includes several species, the largest of which can weigh up to 130 pounds. It is covered with silver scales, horizontal stripes on the sides of its body, and several rows of large, sharp teeth in its mouth. Locals claim to have seen scenes of dog fat carp catching swallows to eat. Originally, this was just a rumor, but in January 2014, scientists recorded this scene with images on an artificial lake in the Suroda Reservoir in Limpopo Province, South Africa, when three swallows skimmed over the water and a dog fat carp jumped out and bit one of them in mid-air.
Pictured: Dog fat carp
In fact, predation on swallows is not an accidental phenomenon. The researchers note that more than 20 similar incidents occur every day. Their local investigation lasted for half a month, and almost 300 swallows went to see God. Think about it, swallows have always been known for their flexibility, the so-called "light as a swallow", the flight speed is not slow, almost 30 kilometers per hour, they can even prey on insects during flight. Can you imagine a brainless fish successfully catching a swallow in flight? If you don't plan beforehand, even a million hopeful jumps out of the water may not be able to catch a swallow.
You know, the difficulty of catching a swallow by a fish is comparable to a human climbing Everest. Even if the dog fat carp clings to the surface of the water and jumps straight when the swallow approaches, like a shark jumping out of the water to catch a seal, it can't catch the swallow because when it rushes into the air, the swallow has already flown away. According to the video, the carp is not vertically jumping. Instead, the carp jumps at a very fast speed directly behind the swallow and catches up with the swallow before falling back into the water.
At this point, I think we can almost conclude that some fish have consciousness and thought, but not all fish have it, which is debatable. From today onwards, if anyone says that fish are very low-level animal forms, we have enough evidence to argue. But, well, I'll still keep eating fish, what about you?
Science has a story, let's talk about it in the next issue.