While your pet fish may appear to be oblivious of your presence, chances are it knows you extremely well and can probably even identify you from a crowd of human faces! At least, that is the conclusion reached by scientists the University of Oxford in the U.K. and the University of Queensland in Australia, following an extensive study of the archerfish, a species of tropical fish that can be found all the way from India to Indonesia, the Philippines, and Australia.
The discovery came as a big surprise given that the ability to distinguish between human faces is a complex task. That’s because we all have the same basic features — two eyes sitting above a nose and a mouth. It’s only the subtle differences that make humans discernable from one another. Since this requires a combination of both visual perception and memory, researchers had always assumed that it is a skill possessed only by those with sophisticated brains, i.e., humans, a few select animals — such as horses, cows, dogs, primates — and some birds, like pigeons.
To test if this hypothesis was accurate, a team of scientists led by Dr. Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, decided to study fish. The aquatic animals have small brains that lack the neocortex, or neocortex-like structure, believed to help recognize the subtle differences between human facial features.
The archerfish was the ideal candidate for the study because of the way it catches its prey. Known as nature’s sharpshooters, the aquatic animals “hunt down” land insects by spitting jets of water at them. The stunned flying bugs fall into the water, where the crafty fish is waiting to devour them. The fact that the archerfish can identify their prey so accurately made the researchers wonder if the fish could be trained to distinguish between humans as well.
The team began by presenting four archerfish with images of two human faces. Initially, the fish spit indiscriminately at both. However, they soon learned that pelting water at the one selected by the researchers earned them a food treat. After that, they focused primarily on that image. The researchers then took the experiment one step further, by introducing 44 other human faces to the mix.
To the researcher’s astonishment, the trained archerfish were able to recall the learned image almost 81% of the time. And this accuracy improved to 86% when the researchers made the identification even harder, by replacing the colored photos with a set of black and white images and concealing the shape of the head.
The results of the study, which were published in the scientific journal Nature.com on June 7, suggest that despite having tiny brains, some fish may have developed high visual discrimination capabilities. While it debunks the previous theory that a sophisticated brain with a neocortex is necessary to recognize human faces, the researchers believe that the fish most likely do not process the faces like human brains do. This means that they do not recognize faces by recalling complex facial information like gender and identity, but more likely by discriminating between intricate patterns. Even so, the fact that these archerfish could “remember” those faces demonstrates that they have an impressive memory for details that lasts much longer than the reputed 3 seconds!
This is not the first time researchers have realized how “smart” fish are. Previous studies have shown that the aquatic animals can distinguish between predators and non-predators, recognize fish they have “socialized” with previously, and even recall complex three-dimensional maps of their surroundings.
The most recent discovery has led the researchers to contemplate the possibility that other species of fish could also be capable of recognizing human faces. That, of course, raises the all-important question – Is your pet fish amongst them? Let us know if you are able to find out!
Resources: nature.com, sciencedaily.com, independent.co.uk, guardian.co.uk