Species studied:

A wide variety of species have been studied by comparative psychologists. However a small number have dominated the scene. Pavlov's early work used dogs, but although they have been the subject of occasional studies since they have not figured prominently; however increasing interest in the study of abnormal animal behaviour has led to a return to the study of most kinds of domestic animal. Thorndike began his studies with cats, but American comparative psychologists quickly shifted to the more economical rat, which remained the almost invariable subject for the first half of the twentieth century and continues to be used. Skinner introduced the use of pigeons, and they continue to be important in some fields. There has always been interest in studying various species of primate; important contributions to social and developmental psycholgy were made by Harry F. Harlow's studies of maternal deprivation in rhesus monkeys. Interest in primate studes has accentuated with the rise in studies of animal cognition. Other animals thought to be intelligent have also been increasingly studied. Examples include various species of corvid, parrots—especially the African Gray Parrot—and dolphins.

Animal cognition

Since the 1980s, comparative psychology has undergone a reversal in its fundamental approach. Instead of seeking principles in animal behaviour in order to explain human performance, comparative psychologists started taking principles that have been uncovered in the study of human cognition and testing them in animals of other species. This approach is referred to as the study of animal cognition. It has led to significant advances in our understanding of concept formation, memory, problem solving and other cognitive abilities in animals.