Abstract: This experiment examines the cues used by cattle to discriminate between people, particularly the role played by facial cues. We trained and tested eight Holstein cows 5 days each week for 2 months. For each cow, we used two people, a rewarder and a non-rewarder, of different size and dressed in overalls of the same colour. The operant chamber was a large box within which stood the two people. The cow could see, smell and touch each person. A lever was placed in front of each person. When the cow pushed the lever in front of the rewarder, it received 75 g of concentrate and nothing when it pushed on the other one. For each test session, the cows made 10 choices. The placement of the people was determined randomly according to the Gellerman series. The success criterion was defined as at least eight correct choices out of 10 trials for two consecutive sessions (binomial law P<0.003). During the shaping, seven cows out of eight learned to press the lever to obtain the food. The cows were then tested in a series of 10 trials with only the rewarder present. Seven out of seven cows succeeded in reaching the success criterion. In experiment 1, both the rewarder and the non-rewarder were present and standing upright at normal height and in full view of the cow. Five out of seven cows achieved the success criterion. In experiment 2, the cows could see only the faces of the two people. None of the cows were able to reach the success criterion. In experiment 3, both people were present standing up and wearing identical masks that completely covered their heads. Five cows out of five achieved the success criterion. In experiment 4, we changed the relative height of the people. Five cows out of five succeeded when the two people stood so they were of equal height but with their faces visible. However, no cows succeeded when the people were both of equal height and had their faces covered. This study suggests that cows seem to use multiple cues to discriminate between people. Cows appear able to use either body height or the face to discriminate between people but use of the face alone is more difficult when the cows cannot see the rest of the body.

Abstract: Two-chick broods of the blue-footed booby,Sula nebouxii, ordinarily exhibit stable dominance-subordinance, with the senior (first-hatched) chick habitually aggressive and the junior one habitually submissive (Nelson 1978,The Sulidae: Gannets and Boobies. London: Oxford University Press). But are both the subordinate and the dominant chick affected in their agonistic tendencies by early social experience? To answer this, we permanently paired subordinate and dominant chicks, 2-3 weeks old, with singletons (chicks lacking experience with a nestmate) by cross-fostering. During the first 4 h after pairing, subordinate chicks were seven times less aggressive than singletons and twice as likely to be submissive; dominant chicks were six times as aggressive as singletons. Although most subordinates consistently lost agonistic encounters during the first 10 days after pairing, the proportion of dominants that won decreased progressively until, by day 6, only about half of dominant chicks were winning. Early social experience has a strong but reversable training effect on both subordinates and dominants. Training as a subordinate showed more persistent effects than training as a dominant, possibly in part because our testing situation perpetuated subordinate training and counteracted dominant training.