If you've ever suspected your loyal pet goldfish is glad to see you, this may not be too far from the truth. Fish, it turns out, have some pretty impressive facial recognition abilities — even if they lack the part of the brain traditionally associated with this skill.
The surprising findings come after scientists at the University of Oxford and the University of Queensland trained tropical fish to identify specific faces with great accuracy. The research was published in the June 2016 issue of the journal Scientific Reports.
"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," zoologist Cait Newport, the study's lead author, said in a press release announcing the study "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."
So just how did scientists know when the tropical fish — they used archerfish in the study — were able to recognize a face? This species has an unmistakable communication tool. Archerfish (Toxotes chatareus) are able to stick their faces out of a river or stream to spit jets of water with the precision of a master dart player, usually aiming at bugs and other prey on low-hanging leaves. During the study, scientists trained the fish to shoot at another kind of "bullseye" — human faces.
Archerfish were presented with a picture of a person's face and taught to spit at the picture as a way to show recognition. Then the fish were shown a series of new faces. The fish were able to choose the, ahem, spitting image out of a lineup of 44 different faces. Archerfish were correct 81 percent of the time in an initial experiment, followed by an 86-percent accuracy rate in a second experiment that standardized the faces for brightness and color. Make sure to check out the experiment in action in the video at the top of this article.
These visual abilities to discern faces using sight alone were once thought to exist only in primates. Primates have a well-developed visual cortex known as a neo-cortex, as do humans. Fish do not have this section of the brain, yet demonstrate high-level facial recognition abilities.
"Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces," said Newport. "The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces."
Maybe that shark in "Jaws" really did have a personal vendetta after all.