Fish do not get much credit for memory skills, but new research shows they can learn to recognise human faces.
Far from having a three-second memory, the study found that tropical archerfish were able to pick out a face they had seen before from a group of 45 faces.
Researchers from Oxford University and the University of Queensland trained their fish to recognise one human face, and then tested them by putting that face in a group with 44 new faces.
Archerfish are so named because they spit streams of water to knock bugs out of the sky.
The researchers used this novel trick and trained the fish to spit water at the face they recognised and disregard all others in the group.
Although this sounds like a fishy tale, it was no fluke. The fish managed to get the right face more than 80 per cent of the time.
When the job was made more challenging, with the faces standardised for brightness and colour, the fish did even better, with 86 per cent accuracy.
Being able to recognise faces "is a surprisingly difficult task", mainly because we must all look the same to a fish, said Dr Cait Newport of the department of zoology at Oxford University.
The assumption has always been that only primates with their large complex brains could accomplish such a thing, she said.
Humans even have a special section of the brain, the neocortex, given over to the recognition of faces, which fish do not have.
The researchers published their findings on Tuesday in the journal Scientific Reports.
They positioned a camera underneath a clear-glass aquarium so that viewers could watch as their fish learned to recognise a face and then chose it again and again even when other faces were shown.
The proof was in the spitting.
“In all cases the fish continued to spit at the face they had been trained to recognise, proving that they were capable of telling the two apart,” Dr Newport said.
The experiments show you do not need a neocortex to recognise a face, the researchers said.
The research suggests there are probably plenty of fish in the sea with similar visual skills.