Study Shows Fish Can Recognize Human Faces

The archerfish (Toxotes chatareus), a species of freshwater tropical fish, can recognize individual people’s faces, shows a new study published in thejournal Scientific Reports. According to the authors, it is the first time fish have demonstrated this ability.

“Being able to distinguish between a large number of human faces is a surprisingly difficult task, mainly due to the fact that all human faces share the same basic features,” said study lead author Dr. Cait Newport, a researcher at the University of Oxford.

“All faces have two eyes above a nose and mouth, therefore to tell people apart we must be able to identify subtle differences in their features. If you consider the similarities in appearance between some family members, this task can be very difficult indeed.”

“It has been hypothesized that this task is so difficult that it can only be accomplished by primates, which have a large and complex brain. The fact that the human brain has a specialized region used for recognizing human faces suggests that there may be something special about faces themselves.”

“To test this idea, we wanted to determine if another animal with a smaller and simpler brain, and with no evolutionary need to recognize human faces, was still able to do so.”

Dr. Newport and co-authors found that fish are capable of discriminating one face from up to 44 new faces.

In the study, archerfish — a species of fish well known for its ability to spit jets of water to knock down aerial prey — were presented with two images of human faces and trained to choose one of them using their jets.

The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognize.

They were able to do this task even when more obvious features, such as head shape and color, were removed from the images.

The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81% in the first experiment and 86% in second experiment.

“Using a two-alternative forced-choice procedure, we show that archerfish (Toxotes chatareus) can learn to discriminate a large number of human face images, even after controlling for color, head-shape and brightness,” the scientists said.

“This study not only demonstrates that archerfish have impressive pattern discrimination abilities, but also provides evidence that a vertebrate lacking a neocortex and without an evolutionary prerogative to discriminate human faces, can nonetheless do so to a high degree of accuracy.”