In a very real sense, psychology is probably as old as humanity. In fact, some scientists have argued that one of the defining characteristics of human beings is the ability to study the behavior of others, imagine oneself in their positions and make predictions about their future behavior based on these insights. Certainly, there is evidence that humans have done just that at least since the dawn of recorded history. Ancient writings from China, Egypt, India, Persia, and Greece all display an intense curiosity about the nature of thought, memory, emotion, sensation, and motivation.

The scientific study of psychology is a much more recent development, however. Many historians date the birth of modern psychology from the founding of the first experimental psychology laboratory by Wilhelm Wundt in 1879. As a science, then, psychology is still relatively young. Yet, over the course of little more than 120 years, it...