Mulcahy, N. J., & Call, J. (2006). How great apes perform on a modified trap-tube task. Anim. Cogn., 9(3), 193–199.
Abstract: To date, neither primates nor birds have shown clear evidence of causal knowledge when attempting to solve the trap tube task. One factor that may have contributed to mask the knowledge that subjects may have about the task is that subjects were only allowed to push the reward away from them, which is a particularly difficult action for primates in certain problem solving situations. We presented five orangutans (Pongo pygmaeus), two chimpanzees (Pan troglodytes), two bonobos (Pan paniscus), and one gorilla (Gorilla gorilla) with a modified trap tube that allowed subjects to push or rake the reward with the tool. In two additional follow-up tests, we inverted the tube 180 degrees rendering the trap nonfunctional and also presented subjects with the original task in which they were required to push the reward out of the tube. Results showed that all but one of the subjects preferred to rake the reward. Two orangutans and one chimpanzee (all of whom preferred to rake the reward), consistently avoided the trap only when it was functional but failed the original task. These findings suggest that some great apes may have some causal knowledge about the trap-tube task. Their success, however, depended on whether they were allowed to choose certain tool-using actions.
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Vlamings, P. H. J. M., Uher, J., & Call, J. (2006). How the great apes (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) perform on the reversed contingency task: the effects of food quantity and food visibility. J Exp Psychol Anim Behav Process, 32(1), 60–70.
Abstract: S. T. Boysen and G. G. Berntson (1995) found that chimpanzees performed poorly on a reversed contingency task in which they had to point to the smaller of 2 food quantities to acquire the larger quantity. The authors compared the performance of 4 great ape species (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) on the reversed contingency task while manipulating food quantity (0-4 or 1-4) and food visibility (visible pairs or covered pairs). Results showed no systematic species differences but large individual differences. Some individuals of each species were able to solve the reversed contingency task. Both quantity and visibility of the food items had a significant effect on performance. Subjects performed better when the disparity between quantities was smaller and the quantities were not directly visible.
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Van Schaik, C. (2006). Why are some animals so smart? Sci Am, 294(4), 64–71.
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Russon, A. E., Handayani, D. P., Kuncoro, P., & Ferisa, A. (2007). Orangutan leaf-carrying for nest-building: toward unraveling cultural processes. Anim. Cogn., 10(2), 189–202.
Abstract: We report an empirical study on leaf-carrying, a newly discovered nest-building technique that involves collecting nest materials before reaching the nest site. We assessed whether leaf-carrying by rehabilitant orangutans on Kaja Island, Central Kalimantan, owes to cultural influences. Findings derive from ca 600 h observational data on nesting skills and nesting associations in Kaja's 42 resident rehabilitants, which yielded 355 nests and 125 leaf-carrying cases by 34 rehabilitants. Regional contrasts with 14 other communities (7 rehabilitant, 7 wild) indicated cultural influences on leaf-carrying on Kaja. Association data showed exceptional social learning opportunities for leaf-carrying on Kaja, with residents taking differential advantage of these opportunities as a function of development, experience, and social position. Juvenile males with basic nesting skills were most influenced by social input. Most (27) leaf-carriers had probably learned leaf-carrying when caged and 7 probably learned it on Kaja. Social priming was probably the main impetus to leaf-carrying on Kaja, by simply prompting observers to copy when leaf-carrying associates collected nesting materials, what they collected, and where they used their collected materials. Implications concern acquisition processes and ontogenetic schedules that orchestrate sets of features-needs or interests, cognitive abilities, social preferences-which enable cultural transmission.
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