DESPITE LACKING THE brain section usually used for the task, a species of tropical fish can tell human faces apart, scientists have discovered.
The ability was demonstrated in experiments with eight archerfish, a fish known for spitting pressurised water jets to shoot prey out of the air.
The sharpshooting fish were taught to spit at pictures of human faces displayed on a computer monitor suspended over their aquarium.
“We were pleasantly surprised at the speed at which the fish learnt, as well as their high degree of accuracy,” said study co-author Cait Newport of the Oxford University’s department of zoology.
The fish, which have excellent vision for hunting, were first introduced to two faces, and conditioned to spit at one of them in exchange for a food reward.
The researchers then tested whether the fish would recognise, and spit at, the familiar face among 44 new ones.
The fish got it right more than 80 per cent of the time.
Even when the scientists testing the fish with black and white images, the fish were capable of finding the face they were trained to identify.
The fish learned the task at different speeds – some needed only one training sessions, while others required up to 17.
“It has been hypothesised that this task is so difficult that it can only be accomplished by primates, which have a large and complex brain,” said Newport.
But the archerfish were able to do this despite not having a neocortex, the most recently evolved part of the human brain, governing sensory perception and language.
Birds are likewise able to recognise human faces, and it was recently discovered that they have neocortex-like structures.
Understanding fish intelligence might help shed light on our own brain function — whether facial recognition, for example, is an innate or learned ability.
The findings suggest “that the discrimination of individuals based on facial features is not unique to humans,” wrote the researchers, “and perhaps human faces themselves are not a particularly special class of objects.”
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