All living beings have consciousness

The fish had noticed something, otherwise they would hardly have acted so strangely. Again and again they rubbed their necks over the bottom of the aquarium - a behavior that was previously unknown from the cleaner wrasse. In between, the animals swam to the mirror that was mounted in their aquarium. Did you look at the brown spot on your neck there? Perhaps you were even wondering about the marking according to the motto: "What do I have there?"

What was actually going on in the cleaner wrasse cannot be answered by the researchers who gave the animals the spot and gave them a mirror in the aquarium. However, based on their data, they can ask provocative questions: Does a cleaner wrasse recognize itself in the mirror? And shouldn't the logical conclusion then be that cleaner fish have an ego-consciousness - something that so far only very few species have been expected to do?

The search for meaningful criteria for the "I"

This is the story of the current study, carried out by a team led by Alex Jordan from the Max Planck Institute for Ornithology in Konstanz, in the specialist magazine Plos Biology published, only ostensibly about cleaner fish and their cognitive abilities. In addition, the biologists raise more fundamental questions, such as when it is possible to speak of ego-consciousness in an animal and whether there are any meaningful criteria and a measurement method for this.

The mirror test that the cleaner fish completed is often used as the latter. An animal is given a color mark on a part of its body that it can only see in the mirror. If, for example, a chimpanzee grabs the stain on his nose, that is proof that he has understood: This guy looking at me from the mirror is me.

Since the psychologist Gordon Gallup developed the mirror test almost 50 years ago, it has been regarded as a kind of litmus test. Whoever wants to get into the circle of that species to which the human being grants an ego-consciousness similar to his own must exist. As it should be for an illustrious club, the number of members is small, many failed the admission test. Chimpanzees were the first to take the hurdle, followed by elephants, dolphins and corvids later.

And now also the tropical cleaner wrasse, five to seven centimeters long? The researchers interpreted the rubbing of their necks as an equivalent reaction to a chimpanzee, for example, who touches the patch of paint with his fingers. As a control, the researchers also gave fish without a spot a mirror in the aquarium and marked some animals with a transparent substance. This should ensure that the treatment itself did not affect behavior. In none of these cases did the fish rub their necks. And when, instead of the mirror, they got a conspecific, separated by a transparent pane, into the pool, they behaved differently than in front of a mirror.

The researchers draw clear conclusions from the fish experiment

However, despite the careful control, objections to the structure of the study can also be cited. Only three out of four fish passed the test. But the small sample size is a problem in many such studies, and the fact that only some of the test subjects come off successfully is also the case with elephants and crows, for example.

The authors draw a clear - and at first glance perhaps surprising - conclusion: They advocate not seeing successful completion of the test "as evidence of self-awareness in cleaner fish". It is questionable whether the mirror test is really suitable with certainty as proof of ego-consciousness. "There isn't one test that makes things so clear," says Jordan. Accordingly, the much-cited mirror test would be far less informative than long thought, and long-cherished views on the self-awareness of other species would also have to be put to the test.

The behavioral scientist Frans de Waal sees it similarly, who himself has done a lot of research on the mirror test and comments on the study as a member of the magazine's scientific committee. He also advocates taking the test less seriously. He is divided, he writes in his book "Are We Smart Enough To Know How Smart Animals Are?": "I do believe that spontaneous self-awareness means something. It could indicate a stronger self-awareness. Nevertheless, I cannot imagine that ego-consciousness is lacking in other species. "

Above all, de Waal criticizes the black and white thinking that often prevails on this topic: either an animal recognizes itself in the mirror and is aware of itself, or not. "Wouldn't it also be possible for self-awareness to develop according to the onion principle instead of appearing all at once?" Countered de Waal.

Awareness can also be seen in the use of joysticks

From an evolutionary point of view, this intermediate theory is plausible and supported by numerous studies with different animal species. Although they do not recognize themselves spontaneously in the mirror, rhesus monkeys, for example, can learn this if the marking is not only visually noticeable, but can also be felt. This can be achieved, for example, with a laser beam that slightly irritates the skin. In addition, rhesus monkeys can easily distinguish whether it is they themselves who are moving a cursor on a screen using a joystick, or whether a computer is taking over control. Capuchin monkeys also fail the mirror test, but still react much more confidently to their own reflection than when they sit across from a conspecific behind a Plexiglas pane. And dogs can at least use a mirror as a tool to find food hidden behind a corner. So there is some evidence that the ability to recognize oneself has developed in stages in the animal kingdom. However, the mirror test alone does not reflect this complexity.

The question that remains is whether any animal, like humans, poses in front of the mirror and stages itself there. After all, it is known of elephants and chimpanzees that they explore their oral cavity in front of the mirror, after all they don't get to see them otherwise. The female orangutan Suma, who lived in the Osnabrück Zoo in the 1970s, went one step further, as behavior researcher Gerti Dücker reported: "Suma put a lettuce leaf on her head and ran with it to a mirror. She sat down right in front of it, watched her headgear and ran her hand over it. "Who knows what was going through her head. Maybe it was the old question: "Am I beautiful?"