Custance, D., Whiten, A., Sambrook, T., & Galdikas, B. (2001). Testing for social learning in the “artificial fruit” processing of wildborn orangutans (Pongo pygmaeus), Tanjung Puting, Indonesia. Anim. Cogn., 4(3), 305–313.
Abstract: 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.
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Russon, A. E., & Galdikas, B. M. F. (1995). Constraints on great apes' imitation: Model and action selectivity in rehabilitant orangutan (Pongo pygmaeus) imitation. J. Comp. Psychol., 109(1), 5–17.
Abstract: We discuss selectivity in great ape imitation, on the basis of an observational study of spontaneous imitation in free-ranging rehabilitant orangutans (Pongo pygmaeus). Research on great ape imitation has neglected selectivity, although comparative evidence suggests it may be important. We observed orangutans in central Indonesian Borneo and assessed patterns in the models and actions they spontaneously imitated. The patterns we found resembled those reported in humans. Orangutans preferred models with whom they had positive affective relationships (e.g., important caregiver or older sibling) and actions that reflected their current competence, were receptively familiar, and were relevant to tasks that faced them. Both developmental and individual variability were found. We discuss the probable functions of imitation for great apes and the role of selectivity in directing it. We also make suggestions for more effective elicitation of imitation. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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