Fish can recognise one human face from another and can tell their owners apart from strangers, new research has revealed.A species of tropical fish were able to distinguish between people – the first time fish have shown such an ability.
The researchers said it is an “impressive” feat, given that it requires sophisticated visual recognition capabilities.
Study author Doctor Cait Newport, of Oxford University, said: “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.
“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.”
The researchers found that fish, which lack the sophisticated visual cortex of primates, are still capable of discriminating one face from up to 44 new faces.
In the study, published in the journal Scientific Reports, archerfish – a species known for its ability to spit jets of water to knock down aerial prey – were presented with two images of human faces and trained to choose one using their jets.
The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognise.
They were able to complete the task – even when more obvious features, such as head shape and colour, were removed from the images.
The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81 per cent in the first experiment.
The figure raised to 86 per cent in the second experiment in which facial features such as brightness and colour were standardised.
Dr Newport said: “Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognising faces.
“Despite this, many fish demonstrate impressive visual behaviours and therefore make the perfect subjects to test whether simple brains can complete complicated tasks.
“The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognise human faces.”
Human facial recognition has previously been demonstrated in birds. But, unlike fish, they are now known to possess neocortex-like structures.