You look familiar Roberto Nistri/Alamy Stock Photo

A little striped fish that lives among rocks in Lake Tanganyika in East Africa has the unexpected ability to recognise individual faces, which it uses to keep menacing strangers in sight.

The cichlid (Julidochromis transcriptus) identifies unfamiliar individuals by looking at the pattern around their eyes rather than at other body parts such as their fins or trunk, researchers have discovered.

While facial recognition has been tested in some mammals, including apes, and in birds, animals such as fish or wasps were erroneously thought to have brains too simple for the task. After recent research showed that aquarium fish can be thought to identify the faces of their human owners, the Tanganyikan cichlid has now demonstrated how facial recognition is used in the wild.


Because the fish lives in rock crevices hidden by vegetation on the lakebed, only a small part of its body tends to be visible at any given time. This prompted the researchers to investigate which body element most attracts the fish’s attention.

“If this fish used only the face to recognise others, that would show that ‘face’ is an important social cue,” says Takashi Hotta of Osaka City University in Japan.

Wary of strangers

The researchers isolated eight adult males from a group of familiar individuals and placed them in a tank. There they were exposed to digital models of other individuals with a combination of familiar and unfamiliar features on their faces and bodies. “We found that our subjects were especially guarded against only unfamiliar face models, regardless of body type,” says Hotta.

The males spent longer following the unfamiliar faces as the model moved around the tank, a sign that they were monitoring a potential threat, using their ability to distinguish unique facial patterns.

“It’s not so much the recognition itself that is difficult, but the fact that they use recognition suggests that they are keeping track of relationships with each other and that’s where things may get complicated,” says Michael Sheehan of Cornell University in New York. This shows a sophisticated processing ability, he says.

“Fish are generally lowly regarded,” says Ken Collins of the University of Southampton, UK. “One example is the widespread but false notion that goldfish only have a 3-second memory.”

However, much like mammals, fish “can have complex lives and consequently need a number of cognitive abilities with which to carry out a range of behaviours”.

Collins notes that the whole field of determining animal intelligence is dogged by a long history of “inappropriate testing ‘proving’ that one species is more intelligent than another”. This is why, he says, “this new research is noteworthy, having devised a valid testing environment extending the recognition capability to a new group”.

Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2017.03.001

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