Psychology has as its aim the understanding of human behavior, and as a secondary goal, the treatment of behaviors deemed abnormal. Almost immediately upon the formation of the field, efforts were made to place psychological studies on a scientific basis. Early psychological studies were conducted by Wilhelm Wundt at the University of Leipzig, Germany. One of his students, G. Stanley Hall, then went on to establish the first American psychological laboratory at Johns Hopkins University.

Then, in 1900, Sigmund Freud introduced psychoanalytical theory in his book “The Interpretation of Dreams.” This was the first ultimately large-scale effort to apply psychological knowledge to the problem of treatment or therapy.

Human psychology and the related fields of psychoanalysis and psychotherapy achieved their greatest acceptance and popularity in the 1950s, at which time they were publicly perceived as sciences. But this was never true, and it is not true today – human psychology has never risen to the status of a science, for several reasons:

Ethical considerations.

If you want to study the behavior of rats or pigeons, there are no significant ethical limitations – you can kill them, you can cut them up, you can dress them out in EEG probes while they play violent video games, no one will complain. They are expendable, they are animals.

But as to the study of human beings, there are severe limitations on what kinds of studies are permitted. As an example, if you want to know whether removing specific brain tissue results in specific behavioral changes, you cannot perform the study on humans. You have to perform it on animals and try to extrapolate the result to humans.

One of the common work-arounds to this ethical problem is to perform what are called “retrospective studies,” studies that try to draw conclusions from past events rather than setting up a formal laboratory experiment with strict experimental protocols and a control group. If you...