Despite having a much simpler and smaller brain than that of primates, fish have the remarkable ability to distinguish between human faces, new research has found. “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 first author Cait Newport from Oxford University. “It has been hypothesised that this task is so difficult that it can only be accomplished by primates, which have a large and complex brain,” Newport noted. To test this idea, the researchers wanted to determine if another animal with a smaller and simpler brain, and with no evolutionary need to recognise human faces, was still able to do so. In the study, archerfish -- a species of tropical 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 recognise. They were able to perform this task even when more obvious features, such as head shape and colour, were removed from the images.
