Fishes And Facial Recognition
Researchers from the universities of Tokyo and Okayama, Japan, studied adult medakas, a type of fish, to identify how the fish recognise other individuals. Understanding this can help us to explain how animals connect to each other in their social worlds.
In many animal social groups, the ability to recognise other individuals correctly is essential for maintaining important social interactions such as pair-bonding, hierarchy, inbreeding avoidance, and recognition of offspring, nest mates, etc. Individual recognition (IR) is thus paramount for maintaining various social interactions in a group. Previous studies have shown that face recognition is one of the most specialised and common cognitive abilities in IR among mammals. However, scientists have long argued that the face-specific processes are unique to humans or shared only by closely related species. The present study is in fact the first explore the face-inversion effect in animals other than mammals.
The researchers found that medaka fish use both vision and smell to distinguish between
other fish, but could recognise each other based on vision alone. More specifically, the fish looked at the faces to tell others apart, and even after black spots were added to their faces, the fish could still differentiate between the others. This suggests that medaka are tolerant to some level of local change during IR, just like we can recognise our old classmates twenty years later. Furthermore, the fish were able to discriminate between two fish and two objects, but failed the task when the fish face images were presented upside-down. This was not observed when two objects were inverted, though. This suggests that just like humans, faces may be special for fish, too.
But how is it that we cannot tell individual fish apart? Surely it cannot be above our cognitive capabilities? The researchers hypothesize that the medaka may distinguish each other with visual cues alone due to differences in sight. They were shown to see light of a broader spectrum compared to humans. This is not the only example of animals being better at differentiating their own, though. Sheep, for example, were shown to discriminate sheep faces with only 5–10% differences – a near impossible feat for humans non-experienced in telling sheep apart.
The findings of this study will enable us to better understand social interactions in fish and, potentially, enhance our knowledge of how our own ability to recognize faces has evolved. Although it is likely that the mechanism behind medaka face recognition differs from that in mammals, animal advocates will benefit from this new similarity bringing the two animal groups, namely fish and mammals, even closer together. It is after all very impressive that brains as small as those of medaka fish are able to manage such a complex cognitive task we too perform daily.