SCIENCE
06/07/2016 12:23 pm ET

Some Fish Can Recognize Human Faces, Scientists Find

Don’t underestimate your pet fish.

Zena Holloway via Getty Images

Even tiny brains can accomplish complex tasks.

Scientists have found that archerfish (a species of tropical fish) can learn to recognize human faces with striking accuracy. The finding, reported Tuesday in Scientific Reports, adds fish to list of animals, including birds, that are capable of pulling off the visual task. Recognizing faces requires such sophisticated cognitive function that it was previously attributed to only humans and other primates with large brains.

“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,” Cait Newport of Oxford University said in a statement. “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.”

Newport told CNN that if the archerfish can tell humans apart, it's possible that other fish can, too.

A. & J. Visage via Getty Images
An archerfish spits a jet of water.

The archerfish knock down insects hovering above them by spitting out a jet of water. This skill also means that the fish have a way of indicating an answer, making them particularly eligible for participating in a lab study.

In the experiments, Newport and her colleagues showed two human images to the fish and trained them to choose one of the images by giving them a treat each time they spit on the correct image.

Next, the fish were presented with the face they’d learned and dozens of new faces. In about 80 percent of the trials, the fish selected the face they already knew. The fish were able to do this task even when the faces were fairly similar, as you can see in this video:

In humans, the brain has a specialized region used for recognizing human faces, known as the fusiform face area, or FFA. The simpler brain of the fish entirely lacks this region, Newport said. Nevertheless, the archerfish that the team studied were capable of choosing the familiar face from up to 44 new faces.

“The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces,” Newport said.

Of course, we humans are still better than fish at facial recognition, thanks to our FFA. “Humans may have special facial recognition brain structures so that they can process a large number of faces very quickly or under a wide range of viewing conditions,” Newport said.

Picking a face out of a crowd doesn’t necessarily mean a fish knows that person, but rather that it can detect and learn subtle differences in visual patterns. In fact, archerfish have already demonstrated great vision by being able to detect small prey against a visually complex background, the researchers said.

Previous research has suggested that birds, and perhaps bees, are able to recognize human faces as well.

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