Comparative Psychology

The comparative study of animal and human cognition should be an important part of cognitive science. The field of comparative psychology, however, emerged from the paradigm of BEHAVIORISM and so has not contributed greatly toward this end. The reasons for this are telling and help to explicate the main directions of modern evolutionary thinking about behavior and cognition.

The general program of comparative psychology began with Charles DARWIN's Origin of Species (1859). Darwin believed that the comparative study of animal behavior and cognition was crucial both for reconstructing the phylogenies of extant species (behavioral comparisons thus supplementing morphological comparisons) and for situating the behavior and cognition of particular species, including humans, in their appropriate evolutionary contexts. Toward these ends, Darwin (1871, 1872) reported some informal comparisons between the behavior of humans and nonhuman animals, as did his disciples Spencer (1894), Hobhouse (1901), and Romanes (1882, 1883). The goal was thus clear: to shed light on human cognition through a study of its evolutionary roots as embodied in extant animal species.

Arising as a reaction to some of the anthropomorphic excesses of this tradition was behaviorism. During the early and middle parts of the century, researchers such as Watson, Thorndike, and Tolman espoused the view that the psychology of nonhuman animals was best studied not informally or anecdotally, but experimentally in the laboratory. Within this tradition, some psychologists became interested in comparing the learning skills of different animal species in a quantitative manner, and this procedure came to be known as comparative psychology. One especially well-known series of studies was summarized by Bitterman (1965), who compared several species of insect, fish, and mammal on such things as speed to learn a simple perceptual discrimination, speed to learn a reversal of contingencies, and other discrimination learning skills. An implicit assumption of much of this work was that just as morphology became ever more complex from insect to fish to mammals to humans, so behavior should show this same "progression" (see Rumbaugh 1970 and Roitblatt 1987 for more modern versions of this approach).

Comparative psychology came under attack from its inception by researchers who felt that studying animals outside of their natural ecologies, on experimental tasks for which they were not naturally adapted, was a futile, indeed a misguided, enterprise (e.g., Beach 1950; Hodos and Campbell 1969). They charged that studies such as Bitterman's smacked of a scalae natura in which some animals were "higher" or "more intelligent" than others, with, of course, humans atop the heap. That is, many of the comparative studies of learning implicitly assumed that nonhuman animals represented primitive steps on the way to humans as evolutionay telos. This contradicted the established Darwinian fact of treelike branching evolution in which no living species was a primitive version of any other living species, but rather each species was its own telos.

Another blow to comparative psychology came from experiments such as those of Garcia and Koelling (1966), which demonstrated that different species were evolutionarily prepared to learn qualitatively different things from their species-typical environments. More generally, many studies emanating from the traditions of ETHOLOGY and behavioral ecology at this same time demonstrated that different animal species were adapted to very different aspects of the environment and therefore that comparisons along any single behavioral dimension, such as learning or intelligence, were hopelessly simplistic and missed the essential richness of the behavioral ecology of organism-environment interactions (see Eibl-Eibesfeldt 1970 for a review). Ethologists and behavioral ecologists were much less interested in finding general processes or principles that spanned all animal species than were comparative psychologists, and they were much less inclined to treat human beings as any kind of special species in the evolutionary scheme of things.

Today, most scientists who study animal behavior have incorporated the insights of the ethologists and behavioral ecologists into their thinking so that it would currently be difficult to locate any individuals who call themselves comparative psychologists in the classic meaning of the term (see Dewsbury 1984a, 1984b for a slightly different perspective). However, there does exist a journal called the Journal of Comparative Psychology, and many important studies of animal behavior are published there -- mostly experimental studies of captive animals (as opposed to ethological studies, which are more often naturalistic). In contrast to the classic, behavioristic form of comparative psychology, modern comparative studies pay much more attention to the particular cognitive skills of particular species and how these are adapted to particular aspects of specific ecological niches. This enterprise is sometimes called COGNITIVE ETHOLOGY.

For these same reasons, modern comparative studies typically compare only species that are fairly closely related to one another phylogenetically -- thus assuring at least some commonalities of ecology and adaptation based on their relatively short times as distinct species. As one example, in the modern study of primate cognition there are currently debates over possible differences between Old World monkeys and apes, whose common ancestor lived about 20 to 30 million years ago. Some researchers claim that monkeys live in an exclusively sensori-motor world of the here-and-now and that only apes have cognitive representations of a humanlike nature (Byrne 1995). Other researchers claim that all nonhuman primates cognitively represent their worlds for purposes of foraging and social interaction, but that only humans employ the forms of symbolic representation that depend on culture, intersubjectivity, and language (Tomasello and Call 1997). These kinds of theoretical debates and the research they generate employ the comparative method, but they do so in much more ecologically and evolutionarily sensitive ways than most of the debates and research in classical comparative psychology.

Comparative studies, in the broad sense of the term, are important for cognitive science in general because: (1) they document something of the range of cognitive skills that have evolved in the natural world and how these work; (2) they help to identify the functions for which particular cognitive skills have evolved, thus specifying an important dimension of their nature; and (3) they situate the cognition of particular species, including humans, in their appropriate evolutionary contexts, which speaks directly to such crucial questions as the ontogenetic mechanisms by which cognitive skills develop in individuals.

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-- Michael Tomasello


Beach, F. (1950). The snark was a boojum. American Psychologist 5:115-124.

Bitterman, M. (1965). Phyletic differences in learning. American Psychologist 20:396-410.

Byrne, R. W. (1995). The Thinking Ape. Oxford: Oxford University Press.

Darwin, C. (1859). On the Origin of Species by Means of Natural Selection. London: John Murray.

Darwin, C. (1871). The Descent of Man and Selection in Relation to Sex. London: John Murray.

Darwin, C. (1872). The Expression of Emotions in Man and Animals. London: John Murray.

Dewsbury, D., Ed. (1984a). Foundations of Comparative Psychology. New York: Van Nostrand.

Dewsbury, D. (1984b). Comparative Psychology in the Twentieth Century. Stroudsburg, PA: Hutchinson Ross.

Eibl-Eibesfeldt, I. (1970). Ethology: The Biology of Behavior. New York: Holt, Rinehart, Winston.

Garcia, J., and R. Koelling. (1966). The relation of cue to consequent in avoidance learning. Psychonomic Science 4:123-124.

Hobhouse, L. T. (1901). Mind in Evolution. London: Macmillan.

Hodos, W., and C. B. G. Campbell. (1969). Scala naturae: Why there is no theory in comparative psychology. Psychological Review 76:337-350.

Roitblat, H. L. (1987). Introduction to Comparative Cognition. New York: W. H. Freeman and Company.

Romanes, G. J. (1882). Animal Intelligence. London: Kegan, Paul Trench and Co.

Romanes, G. J. (1883). Mental Evolution in Animals. London: Kegan, Paul Trench and Co.

Rumbaugh, D. M. (1970). Learning skills of anthropoids. In L. A. Rosenblum, Ed., Primate Behavior: Developments in Field and Laboratory Research. New York: Academic Press, pp. 1-70.

Spencer, H. (1894). Principles of Psychology. London: Macmillan.

Tomasello, M., and J. Call. (1997). Primate Cognition. Oxford University Press .