Wang Makigei Researcher (currently a specially appointed researcher at the Graduate School of Arts and Sciences, the University of Tokyo) and a research group at Okayama University are using "face" information to identify their peers. It was discovered that there is a psychological phenomenon "inverted face effect" that reduces the ability to distinguish faces when presented upside down.This is the first time that an animal other than mammals has shown an "inverted face effect".
Many animals, including humans, have the ability to identify peers of the same species.In the case of humans, the mechanism for recognizing the face is specialized, and when looking at the face, the information on the entire face is read instead of focusing on specific parts (eyes and nose).However, when the face is turned upside down, the mechanism for recognizing the entire face does not work, and the "inverted face effect" is observed in which the ability to distinguish the face is reduced.
So far, there have been few reports of this "inverted facial effect" tested in animals other than mammals.On the other hand, it was confirmed that some fish such as killifish also have the ability to distinguish fellow fish, but the key information for females to distinguish multiple males was unknown.
Therefore, the study found that the visual information of the "face" is particularly important when the female of the medaka is "matched" with the male who hides a part of the body and the female distinguishes the male.When the female met the male with the face (head) hidden, the female could not distinguish the "male who was watching", but when the tail was hidden, it could be identified.
In addition, when the male was presented upside down and upside down using a prism, it was possible to distinguish it when it was upside down, but it was not possible to distinguish it when it was turned upside down.These experiments suggest that medaka also have a specialized face recognition mechanism, and this study shows for the first time that the "inverted face effect" can be seen in fish that are evolutionarily far from humans.
By elucidating the neural mechanisms of face recognition and individual memory with medaka, it is expected that this research will be the evolutionary origin of the face recognition mechanism, which is important for the establishment of animal society.