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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 8, Issue 2, 1995


Acquisition and Comprehension of a Tool-Using Behavior by Young Chimpanzees (Pan Troglodytes): Effects of Age and Modeling


acquisition of a tool-using ability was investigated in six young chimpanzees (Pan troglodytes, 2 to 4 years old). Age-matched pairs were presented with a horizontal transparent tube with a food item inserted in the center, and a wooden tool. Insertion of the tool into the tube was required in order to obtain the food item. One of each pair was exposed to a model performing the task successfully,whereas the age-matched peer was not. Following acquisition, subjects were tested with more complex versions of the task to evaluate their comprehension. Age affected acquisition; older individuals learned to solve the task in fewer number of trials than younger chimpanzees. The presence of a model influenced acquisition only in the 3-and-4 year-old groups and not in the 2-year-old group. Moreover,older individuals made fewer errors when faced with tools requiring modification, and the performance of older individuals on these complex tasks improved with limited practice. These results are related to recent findings on cognitive development in chimpanzees indicating that self-recognition emerges between 24 and 30 months and that 4 year-old chimpanzees can imitate novel arbitrary actions. Comparisons with human cognitive developmental data and findings on the same task with older apes point to the link between the emergence of imitation, self recognition, and comprehension of the cause-effect relation present in this task. Competence in all these domains is somewhat delayed in chimpanzees compared to humans.

Jumping Spiders Alternative Turns in the Abscence of Visual Cues


abilities of four species of diurnal jumping spiders (Helpis minitabunda,Portia fimbriata, Trite auricoma, and Trite planiceps) and one species of nocturnal clubionid spider (Clubiona cambridgei) to maintain approximately straight paths by alternating turns in the absence of visual cues was investigated. Under infra-red light (observed using infra-red video), individual spiders were run rough a maze comprising a single forced turn and then a choice of turning in the same or opposite direction to the forced turn. At the second (free) turn, each species turned in the direction opposite to the forced turn (i.e., alternated turns) more frequently than it turned in the same direction. There was no evidence that species differed in tendency to alternate turns. In nature, jumping spiders may use this ability to navigate in the absence of visual cues when foraging or escaping predators in darkness. It is suggested that alternation of turns by jumping spiders depends on proprioceptive information gathered during previous turns.

Attractiveness of Composite Faces: A Comparative Study


are presented which give cross cultural generality to the observation by Langlois and Roggman (1990) that young southwest American college students found composite faces more attractive than the individual faces from which they were derived. These authors attributed the phenomenon to a cognitive mechanism of prototypicality originating in an evolutionary process of stabilising selection towards facial averageness. In this study New Zealand Caucasian and New Zealand Chinese students, together with indigenous students in China, Nigeria and India chose composite New Zealand Caucasian faces as more attractive than the individual faces from which they were constructed. The preference was greater for female than for male faces. Caution is expressed over attributing the phenomenon  to either typicality or stabilising selection.


Book Review -- The Complete Red Ape


in Borneo by Gisela Kaplan and Lesley J. Rogers. University of New England Press, 1994.