Understanding human behavior involves problems infinity more difficult than landing a man on the moon or unravelling the structure of complex molecules. The problems are also more important and more urgent. If we are to tackle them, we must every source of evidence available to us. Studies of animals are one so much source. Sometimes they help just because animals are different and permit the study of issues in a simplified, isolated or exaggerated form. They may assist us in understanding the behavior of man not only through factual comparison between animal and man, but also by helping us to refine the categories and concepts used in the description and explanation of behavior and social structure. But the use of animals involves dangers: it is so easy to make rash generalizations, to slip from firm fact to flight of fancy, to select examples to fit preconceptions. Studies of animals must therefore be used circumspectly, and their limitations of their usefulness specified.