“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,” Dr. Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, and first author of the study, explained 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. If you consider the similarities in appearance between some family members, this task can be very difficult indeed.”
Even humans have trouble picking out other humans in a lineup, and we actually have a region in our brains that deals with facial recognition, known as the fusiform face area. The brain of the archerfish lacks this region, yet, it can recognize a familiar face 80 percent of the time.
“The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces,” Newport said.
The archerfish has a unique skill, where it spits a jet of water at insects hovering above, knocking them down. Researchers used this ability to help indicate an answer from the fish. The team would show two human faces to the fish and trained the fish to select one of the faces by giving it a treat each time it spit on the correct one.
After learning the face, the researchers presented the fish with 44 new faces and the fish continued to spit at the face it was conditioned to recognize with a high degree of accuracy.
“This study not only demonstrates that archerfish have impressive pattern discrimination abilities, but also provides evidence that a vertebrate lacking a neocortex and without an evolutionary prerogative to discriminate human faces, can nonetheless do so to a high degree of accuracy,” the researchers wrote in their study.
It suggests that even small brains can distinguish between different faces. Humans are unique in that we evolved with these brain structures, which allows us to process a large number of faces. This fish may be able to pick out a face it knows out of a small lineup, but whether it can pick the same face out of a crowd remains uncertain.