New study shows that fish can recognize human faces

Fish recognize faces
CC BY 2.0 Benson Kua/flickr

Think your pet fish knows it’s you? It's quite possible he does.

Most of us can tell one face from the next. The capacity is built into our brains; primates can do this, we know our dogs can do it, and research has shown that birds can as well.

But fish?

According to a new study from researchers at the University of Oxford and the University of Queensland, for the first time a species of tropical fish has been shown to be able to tell the difference between human faces.

The team proved that archerfish (Toxotes chatareus) were able to learn and recognize faces with a surprising level of accuracy, a feat that depends on sophisticated visual recognition capabilities. And not only that, but they could distinguish one face from 44 new ones – that’s better than many of us could do! Lead author Dr. Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, says:

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. 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.

Also remarkable is the level of training the fish were able to achieve. The archerfish employed in their research is a species of tropical fish that spits a jet of water in the air to knock insects out of branches for food. The fish were given two images of faces set above the tanks, and were trained to select one of them by squirting it with their jets. That alone is pretty cool.

The fish were then given an array of new faces and were able to correctly aim their water jet at the face they had learned. They were able to do this among 44 new faces; and they were able to do this even when the head shapes were made the same and the color was removed from the photos.

The fish were uncannily correct when picking the right face, reaching an average peak performance of 81 percent when selecting the known face from 44 others, and 86 percent when selecting the known face after the features were standardized.

Newport says, “Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces. Despite this, many fish demonstrate impressive visual behaviors and therefore make the perfect subjects to test whether simple brains can complete complicated tasks.”

So maybe we consider their brains to be simple, but for an animal unlikely to have evolved the ability to distinguish between human faces to be able to learn this, they’ve definitely got something going on in there.

Tags: Animals | Fish | Oceans

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