of Bottlenosed Dolphins
Louis M. Herman
Kewalo Basin Marine Mammal Laboratory
and Social Science Research Institute,
University of Hawaii
Like any biological trait, cognitive characteristics may vary widely across species. A fundamental task for comparative psychologists and cognitive ethologists (see Griffin, 1981) is to describe these characteristics for any species of interest. The goals of the description are to understand the general and specific structures and processes of cognition, the dimensions of cognition, its continuities and discontinuities across species, how the described cognitive characteristics for given species may relate to the ecological and social pressures of that species' natural world, and what pressures may select for the evolution of particular cognitive traits.
The bottlenosed dolphin (Tursiops truncatus) is a compelling subject for study of animal cognition. The absolute and relative size of the bottlenosed dolphin brain, as well as its architecture and apparent complexity ( Flanigan, 1972; Morgane , 1978; Morgane & Jacobs, 1972; but see Morgane, this volume), suggest exceptional information-processing power. Jerison ( 1973) has proposed that information-processing power, or biological intelligence, is indexed by the degree of encephalization of the brain--the "residual" mass of the brain not accounted for by body size nor mapped onto the control of basic biological functions. It is therefore noteworthy that encephalization in the bottlenosed dolphin may be comparable to that of living species of higher primates including humans ( Jerison, 1978). Nevertheless, in the final analysis, intellectual performance, rather than structural criteria, defines the quality of a brain. This chapter reviews current knowledge of intellectual performance and related cognitive characteristics in bottlenosed dolphins, as obtained through laboratory studies.