The effort to understand human behavior must itself be one of the oldest of human behaviors. But for all the centuries of effort, there is no compelling evidence to convince us that we do understand human behavior very well. The application of that reasoning and of those procedures which together we call "the scientific method" to the understanding of human behavior is of relatively recent origin. What we have learned about human behavior in the short period-let us say from the founding of Wundt's laboratory in I-eipzig in 1879 until now-is out of all proportion to what we learned in preceding centuries. The success of the application of sci- entific method to the study of human behavior has given us new hope for an accelerating return of knowledge on our investment of time and effort. But most of what we want to know is still unknown. The application of
scientific method has not simplified human behavior. It has perhaps shown us more precisely just how complex it really is.