The average sheep has long been judged a placid and dim-witted creature, a view epitomised by Sir Winston Churchill when he labelled Clement Attlee a "sheep in sheep's clothing".
But a study by Cambridge University suggests that we may have underestimated their intellectual capacities. Sheep can recognise human faces, spot the facial features of their handlers, and can even distinguish newsreader Fiona Bruce from actress Emma Watson.
In experiments in which the animals were rewarded with food for picking out portraits of Bruce, Watson and Barack Obama, sheep proved they were experts at identifying individuals.
In fact, they could even recognise people when pictures were altered or were taken from a different angle, an ability only previously recorded in humans and primates. And when shown pictures of their handlers without any training, the sheep did a double take then wandered over to their image.
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"Anyone who has spent time working with sheep will know that they are intelligent, individual animals who are able to recognise their handlers," said Prof Jenny Morton, who led the study.
"We've shown with our study that sheep have advanced face-recognition abilities, comparable with those of humans and monkeys. Sheep are long-lived and have brains that are similar in size and complexity to those of some monkeys."
The ability to recognise faces is one of the most important human social skills. People recognise familiar faces easily, and can identify unfamiliar faces from repeatedly presented images.
As with some other animals such as dogs and monkeys, sheep are social animals and can recognise other sheep as well as familiar humans. But little is known about their overall ability to process faces. Researchers from Cambridge's Department of Physiology, Development and Neuroscience trained eight sheep to recognise the faces of four celebrities from photographic portraits displayed on computer screens. Training involved the sheep making decisions as they moved around a specially-designed pen.
At one end of the pen, they would see two photographs displayed on two computer screens and would receive a reward of food for choosing the photograph of the celebrity, by breaking an infrared beam near the screen. If they chose the wrong photograph, a buzzer would sound and they would receive no reward. Over time, they learn to associate a reward with the celebrity's photograph. After training, the sheep were shown two photographs - the celebrity's face and another face. In this test, sheep correctly chose the learned face eight times out of 10. In these initial tests, the sheep were shown the faces from the front, but to test how well they recognised the faces, the researchers next showed them the faces at an angle.
As expected, the sheep's performance dropped, but only by about 15 per cent - a figure comparable to that seen when humans perform the task.
Finally, the researchers looked at whether sheep were able to recognise a handler without pre-training. When a portrait of the handler was interspersed randomly, the sheep chose them seven out of 10 times. The research was published in the journal Royal Society Open Science.
- The Telegraph, London