But a study by Cambridge University suggests that we may have underestimated their intellectual capacities. "I wanted people that the sheep had not met (I am very sure of this)". The animal was given a cereal pellet as an award if it approached the correct image.
The sheep would nuzzle up close to their chosen screen, where they would trigger an infrared sensor releasing a treat, if they had chosen correctly. Eight times out 10 the sheep picked the celebrity.
To challenge the sheep even further, scientists showed them the same celebrities in photos captured from a different, tilted angle. (A sheep might have had to select Emma Watson vs. a football helmet or gas lamp, for instance.) The third test pitted the sheep's celebrity targets against unfamiliar humans.
In a fifth, and final task, the sheep were shown a photograph of their day-to-day handler - who they know well but have never seen a picture of - next to that of an unknown person.More news: WWE SmackDown: SHOCK Title Change In UK
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Sheep have been known to pick out pictures of individuals in their flock, and even familiar handlers (SN: 10/6/12, p. 20).
"Our study gives us another way to monitor how these abilities change, particularly in sheep who carry the gene mutation that causes Huntington's disease", she pointed out. "This current study adds an interesting new ability to the surprising wide repertoire of behaviour of sheep". People recognise familiar faces easily, and can identify unfamiliar faces from repeatedly presented images.
Sheep join the small group of animals shown to recognize human faces, including monkeys, dogs and horses. "Either the human face is similar enough to the sheep face that [it] activates the sheep face-processing system, or human-face recognition relies on more general-purpose recognition systems".
The study feeds into ongoing research on treating neurodegenerative diseases such as Huntington's, in which face perception can be impaired.