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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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Custance, D., Whiten, A., & Fredman, T. (1999). Social learning of an artificial fruit task in capuchin monkeys (Cebus apella). J. Comp. Psychol., 113(1), 13–23.
Abstract: Social learning in 11 human-raised capuchin monkeys (Cebus apella) was investigated using an artificial fruit that was designed as an analogue of natural foraging problems faced by primates. Each subject observed a human model open each of 3 principal components on the fruit in 1 of 2 alternative ways (“morphs”). The capuchin monkeys reproduced, to differing extents, the alternative techniques used for opening 1 component of the task (poking vs. pulling while twisting out a pair of smooth plastic bolts) but not the other 2. From the subjects' actions on the bolt latch, independent coders could recognize which morph they had witnessed, and they observed a degree of matching to the demonstrator's act consistent with simple imitation or object movement reenactment (A learns from watching B how an object, or parts of an object, move). Thus, these capuchins were capable of more complex social learning than has been recently ascribed to monkeys. (PsycINFO Database Record (c) 2016 APA, all rights reserved)
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Whiten, A., Custance, D. M., Gomez, J. C., Teixidor, P., & Bard, K. A. (1996). Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes). J Comp Psychol, 110(1), 3–14.
Abstract: Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2-4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild.
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