Testing for social learning in the "artificial fruit" processing of wildborn orangutans (Pongo pygmaeus), Tanjung Puting, Indonesia.

Social learning about actions, objects and sequencing was investigated in a group of 14 wildborn orangutans (four adult females and ten 3- to 5-year-old juveniles). Human models showed alternative methods and sequences for dismantling an artificial fruit to groups of participants matched by gender and age. Each participant received three to six 2-min trials in which they were given access to the artificial fruit for manipulation. Independent coders, who were unaware of which method each participant had seen, gave confidence ratings and collected action frequencies from watching video recordings of the experimental trials. No significant differences were found between groups in terms of the coders' confidence ratings, the action frequencies or the sequence of manipulations. These negative results may at least partly reflect the immaturity of a large proportion of the participants. A positive correlation was found between age and the degree of matching to the method shown. Although none of the juveniles succeeded in opening the "fruit", two out of the four adults did so and they also seemed to match more closely the sequence of elements touched over successive trials. The results are compared with similar data previously collected from human children, chimpanzees, gorillas, capuchin monkeys and common marmosets.

Does visual perspective matter in imitation?

Theories purporting to explain the cognitive processes underlying imitation and its taxonomic distribution have proliferated in recent years but a common assumption is that imitators must adopt a model's mental or visual perspective. Data on thirty-six adult subjects were used to test the hypothesis that imitative learning of knots would suffer a decrement proportional to the disparity of visual perspectives on the task that the subject held between observation and performance. There was no significant effect of visual perspective on performance, nor was there a trend in the predicted direction. This was in spite of significant preferences on the part of subjects for minimising the angle of disparity, assessed both by their behaviour and introspective report. The cognitive basis for human imitation is discussed in the light of these findings.