Scientists previously believed that only a few mammals had large enough brains capable of recognizing faces. A few species of birds have also been found to have “neo-cortex like structures” that help in human facial recognition. However, a new study conducted by researchers at the University of Oxford suggests that large and complicated brains are not necessary to recognize human faces. Scientists found that the archerfish could recognize human faces out of a crowd with a high degree of accuracy.
Archerfish have no evolutionary need to recognize humans
Findings of the study were published in the journal Nature Scientific Reports. It is the first time fish have been found to possess facial recognition capabilities. The archerfish, Toxotes chatareus, is a tropical fish distinguished by its black and silver striped scales. Its brains are far simpler than that of humans. They even lack the part of the brain that researchers associate with facial recognition in humans.
Dr. Cait Newport, the lead author of the study, said in a statement that the archerfish have “no evolutionary need to recognize human faces.” These fish have an incredible ability to spit. They shoot jets of water to knock the prey out of the air. That’s why Cait Newport and her colleagues chose the archerfish for the experiment. Scientists first trained the fish to spit on a particular face displayed on a monitor. The fish would be rewarded with food when it got it right.
What happened when the images were changed to black & white?
Next, researchers mixed that face with as many as 44 others. And the fish was able to spit on the correct face 81% of the time. Newport even tried changing the images to black & white and standardizing the head shape to reduce the distinction between various faces. In that test, the fish picked out the correct face 86% of the time. Such a high degree of accuracy suggests that it was not spitting randomly.
Dr. Cait Newport said distinguishing between a large number of human faces is a difficult task because all human faces share the same basic features: a mouth, a nose and two eyes. The fish was able to identify subtle differences in their features to recognize the correct face.