Remembering ewe

Natural History, Feb, 2002 by T.J. Kelleher

Sheep have long been regarded as lost without a guide, ready prey for sly foxes and wolves in familiar clothing. But recent research demonstrates that rather than being stupid, they might have elephantine memories.

Keith Kendrick and colleagues at the Babraham Institute near Cambridge, England, worked with a group of twenty sheep and taught them to recognize frontal views of the faces of twenty-five pairs of their fellows by associating one of each pair with a food reward. (The sheep were considered to have learned when they chose the reward face 80 percent of the time.) The perceptive ruminants could stilt discriminate between the members of the twenty-five pairs up to 800 days after the training period (although in the final 200 days, they made the correct selection less frequently). The test animals were also able to discriminate between profile views of the same faces without being retrained, and they could correctly choose a reward face out of novel pairings of the animals' original mug shots.

The researchers also recorded brain cell activity during these experiments and found that sheep could recall familiar faces after separations of up to twelve months. When presented with pictures of the faces of sheep--and of humans--that either had been or were currently part of the test animals' social groups, the sheep's brains showed increased activity in the same subgroup of cells that encode memories of faces in monkeys and in humans. The sheep vocalized the same way when looking at pictures of former social group members as they did when shown pictures of current ones.

According to the Oxford English Dictionary, "sheepish" has meant "silly" since the fourteenth century. Use it if you must, but don't do it around sheep--who knows how long it takes them to forget an insult? ("Sheep Don't Forget a Face," Nature 414, 2001)