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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 10, Issue 1, 1997


The Logic of Searches in Young Children (Homo Sapiens) and Tufted Capuchin Monkeys (Cebus Apella)

Nine young

children and five tufted capuchin monkeys {Cebus apella) were tested on tasks involving a search for an object hidden within a set of plastic cups. As viewed, the sequences of displacements enabled subjects to eliminate some of the possible locations where the object lay hidden, thereby constraining the search space. Both species deployed principled modes of search, in contrast to a random selection strategy. However, no subject from either group proved able to fully constrain the search on the basis of all of the information conveyed over the full menu of tasks. The reasons for incomplete success are as yet unclear, however failures may be due as much to social limitations as to other forms of error. On that basis we conclude that new paradigms are necessary, designed specifically to evaluate competencies for socially based knowledge on the one hand and self-directed search on the other. 

Brain Dimorphisms and Sex: A Review


this article we review evidence from studies of fish, amphibians, reptiles, birds and mammals which bears on the question of whether differences in sexual behaviour are reflected by differences in central nervous system (CNS) structure. Neural structures in fish demonstrate the existence of both inter- and intra-sexual dimorphisms related to dimorphic behaviours, as well as environmentally triggered changes in the size of neural structures. Seasonal changes in neural structure in amphibians have demonstrated a strong correlation between sexually dimorphic brain structures and sex-specific behaviours. While in reptiles there are some examples of sexually dimorphic CNS structures, C.uniparens demonstrates that differences in brain morphology are not necessary to display sexually distinct behaviour. Birds demonstrate the clearest sex related brain-behaviour differences; the song control nuclei exhibit substantial differences in size between the sexes varying in magnitude in relation to the amount of sexual dimorphism in song production. There are sexually dimorphic areas in the mammalian brain, in areas associated with sexual and maternal behaviour, which  are correlated with differences in hormonal environments during ontogeny. No single phyletic trend is obvious, though this could be the consequence of a small number of taxa examined or the different aims of the studies. It appears that sexuality has not necessarily evolved linearly from a particular primitive vertebrate ancestor but is manifested variously in different vertebrate classes, most likely as the result of distinct environmental pressures.