Archerfish Study: Fish Recognize Faces

By on July 20, 2016
fish recognize faces

We’ve covered the amazing spitting abilities that archerfish have, as the tiny tropical fish are capable of hitting prey both near and far with water jets that hold the same amount of force. But we can now add to that ability the fact that these fish recognize faces. Researchers at Oxford University made the discovery that marks the first time fish have proved they can discern between human faces.

Archerfish used in the study were able to learn and recognize faces with a great deal of accuracy, something that is difficult because of the complex visual recognition at play. Birds are the only other animals shown to be able to recognize human faces.

In the study, archerfish were recorded by underwater cameras that logged their actions from below. The fish 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.

The fish were able to recognize faces even when more obvious features, like head shape or color, were removed from the images. The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81 percent in the first experiment that involved picking the right face from 44 others. In a second experiment, in which brightness and colors were made standard between the images, that identification rate went up to 86 percent.

The ability to distinguish between such a large number of human faces is a very difficult task for animals other than primates because human faces share the same basic features. They all have two eyes above a nose and mouth, with differences only apparent in other relatively small ways.

We humans have no problem identifying faces because our brains have evolved over time to develop the parts necessary for doing it, our neocortex. But fish don’t have this cortex. Despite that, archerfish were capable of discerning one face from more than 40 new faces.

The results help show that even simple brains can complete complicated tasks and suggest that complicated brains are not necessarily needed to recognize human faces. We may only have special structures for facial recognition in our brains so that we can process a large number of faces in rapid order.

“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,” scientists write in a research article detailing the study published in the journal Scientific Reports.

Top image: An archerfish shoots water at an image after being trained to identify human faces. (Credit: Oxford University)

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