When two American astronautsd landed on the moon in the summer of 1971, their activities included an interesting and, for some, surprising demonstration. They showed that when the effects of friction are eliminated, a light object (a feather) and a heavy object (a hammer) will reach the ground at the same time when dropped simultaneously from the same height. This verification of a basic principle of high school physics delighted many viewers of the live televised broadcast, but probably few of them considered the fact that for hundreds of years before Galileo (who is thought to have predicted this outcome originally), Western scholars had accepted Aristotle's hypothesis that heavy objects would fall faster than lighter ones. For most of us, Aristotle's assumption seems intuitively correct, even though we know that it is contrary to scientific theory and empirical fact. Not all scientifically demonstrated phenomena contradict “common sense” intuitions in this way, but this case serves to illustrate the difference between science and intuition as bases of understanding the physical and social world.
The emphasis on subjecting all theoretical concepts, hypotheses, and expectations to empirical demonstration—that is, of testing our ideas—is basically what distinguishes the scientific method from other forms of inquiry. And the principles of scientific methodology, which lend structure to the manner in which such inquiries occur, is what this book is all about. More specifically, this book is intended to represent broadly the methods that have been derived from basic principles of scientific inquiry and to show how they apply to the study of human cognition, affect, and behavior in its social context.
It is important to understand that the research principles and techniques presented throughout this text are not reserved solely for the investigation of scientific theories. At issue, in many instances, are questions of a more personal nature—the consensus surrounding one's personal beliefs, the relative quality of one's performance, the wisdom of one's decisions—and in these circumstances, too, the application of the scientific method can prove useful. At first glance, using scientific principles to guide one's own decision-making