Robert B. Zajonc
Robert Zajonc argues that social psychology, like psychology itself, is not a cumulative science. In physics, biology, geology, and other branches of the natural sciences, there is a consensus as to "the core subject matter of their inquiry"; in social psychology no such consensus exists. Zajonc believes that this lack of agreement derives from "a schism in our conceptions about the basic nature of the individual" -- specifically, the assumption of the rationality of humans. The rationalists, he says, believe that behavior is under the control of voluntary and willful reason; the irrationalists do not. He illustrates this schism by reviewing and classifying some of the most significant social psychological researchers over the past century. These differing views of human nature underlie the noncumulative history of the first century of social psychology. Zajonc maintains that social psychology must come to understand the realms of rationality and irrationality in human nature if it is to proceed in a cumulative fashion.
Two features characterize most sciences. First, they are cumulative. Their progress is fairly linear, and there is a way of knowing what the next problems are. In most fields textbook chapters follow in very much the same order. But social psychology (like psychology itself) is not cumulative. You can take any text in social psychology and shuffle the chapters at random without losing coherence. There is no compelling order. Zimbardo could rearrange the chapters of his splendid textbook in many different ways without loss of sales or intellectual quality.
Second, the scientists of a given discipline agree about the core subject matter of their inquiry. Physicists agree that physics is mostly about matter and energy, biologists agree that they study life and its processes, demographers agree that they study populations, and geologists agree that they are committed to the study of minerals. This is not to say that in any of these fields scholars believe they have the final answer. Physicists do not believe that they fully understand the nature of