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Humans (Homo sapiens) and squirrel monkeys (Saimiri sciureus) were tested for memory of upright and inverted primate faces. Working memory was tested in Experiment 1 with a delayed matching-to-sample procedure, and reference memory was examined in Experiment 2 by requiring subjects to learn to discriminate between successive pairs of upright or inverted pictures. Both human and monkey subjects showed better working memory for upright than for inverted human faces and better reference memory for upright than for inverted human and great ape faces. In Experiment 3, reference memory tests with pigeons (Columba livia) showed no effects of inversion on rate of learning with face pictures. We argue that these findings cannot be explained easily by an individual primate's lifetime experiences with primate faces. We suggest that similar evolved mechanisms for primate face recognition in people and monkeys are responsible for the pattern of data reported.

Rats were trained to discriminate between boxes covered with distinctive odors. There were six stimulus odors, labeled A through F, and the problems learned formed the five premises A+B-, B+C-, C+D-, D+E-, and E+F-. Combining the premises, the relative values oft/Ie stimuli wereIn two experiments, linear arrangement groups learned these premises with Boxes A through F placed in a linear spatial sequence. Nonlinear groups had boxes either randomly changed from one position to another (Experiment 1) or placed in a eircular arrangement (Experiment 2). Tests of transitive inference between the Band D stimuli were carried out in an environment different from that in which premise training took place. Only the groups trained with a linear arrangement of boxes showed evidence of transitive inference. These findings offer support for a spatial coding hypothesis of transitive inference in animals.

We studied central-place foraging in rats (Rattus norvegicus) by placing food items that varied in size and weight at the ends of a 4-arm radial maze. In Experiments 1-3, rats increasingly tended to carry food to the center of the maze as the size of those items increased. Very large food items often were hoarded in the center. Rats consumed food faster on the arms than in the center, and rats traveled faster when carrying food than when not. Blocking arm entrances increased travel time between the center and the arms and decreased food carrying at every item weight except the largest. In Experiments 4-6, important conditions that influence the degree of food-carrying behavior were discovered; these were the intersection of maze arms, the presence of a conspecific, and the use of open vs. closed maze arms.

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