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Roosters in the experiment: failed the classic test
Photo: Sonja Hillemacher / Uni Bonn / dpa
In addition to chimpanzees, dolphins and magpies, roosters may also be able to recognize themselves in the mirror – at least if the mirror test for self-recognition is carried out in a modified form. This was reported last week by a German research team in the journal PLOS One.
Developed in the early 1970s, the Spiegel or Mark test is intended to provide information about the self-perception of a test subject. To do this, a mark is placed on a part of the body that it can only see in the mirror, and then the behavior is observed: If the test subject explores the marked spot on the body in front of the mirror or tries to rub it off, this is considered evidence that he recognizes his reflection as himself.
Animals might feel uncomfortable in the "artificial" experimental environment
Children pass this test from the age of 24 months, but there are only a few successful species in the animal kingdom. Some great apes such as chimpanzees and orangutans pass the test, as do dolphins, Asian elephants and magpies. However, other animal species, which could be expected to recognize their faces in the mirror due to their cognitive abilities, fail.
This could also be due to the fact that the animals feel uncomfortable in the "artificial" experimental environment, speculate researchers from the Universities of Bonn and Bochum, who carried out the mirror test with roosters. In the classic version, the roosters actually did not pass the test, so the scientists changed the experimental set-up.
The researchers wanted to take advantage of a natural behavior for the experiment: "Some chickens, but especially roosters, warn their conspecifics by special calls when a predator – such as a bird of prey or fox – appears," says co-author Onur Güntürkün from the University of Bochum. It is quite different when the animals are alone: then they remain silent so as not to attract the attention of the predator. "The alarm call is the perfect behavior to integrate into an ecologically better adapted test for self-knowledge," explains Güntürkün.
First, the research team tested whether these behavioral differences really showed up in the birds by projecting a bird of prey onto the ceiling in a test arena in which roosters were either alone or separated by a grid with a conspecific. They repeated this experiment three times with each of the 58 roosters. The result: In the presence of a conspecific, the roosters emitted 77 alarm calls, but only 17 on their own. However, the result shows that most roosters actually warn in the presence of a conspecific, when a predator is on the move."
Mirrors instead of grilles
In the next step, the researchers replaced the grid with a mirror and repeated the experiment three times with each animal. In this arrangement, only 174 warning calls were sounded out of 25 attempts. "This proves that the roosters did not identify a conspecific," says Hillemacher. The result is an indication that the roosters may be recognizing themselves in their reflection.
Likewise, there could be another reason why the warning call did not come. For example, the roosters may have seen a strange animal in their image, "which does not behave normally and imitates all movements and thus causes a muffled reaction," according to the study.
In addition, the presentation of a predator, which must be quickly identified in nature, requires rapid information processing in the brain. "This time pressure in information processing could also lead to a lack of or little reactivity towards the 'stranger' in the mirror," the authors continue.
Regardless of this, the scientists see clear indications in their results that the classic mirror-labeling test produces more reliable results if the behavior of the respective animal species is taken into account more strongly – an approach that could also be important for other species.
dpa/ani