Psychology is concerned with studying and, hopefully, understanding human nature, behaviour and the workings of the brain. Our concern, here, is with the way in which psychology goes about its business.
For better or worse, the approach of mainstream Western psychology to studying and understanding human behaviour is essentially a scientific one. When psychology first emerged from philosophy in the latter part of the 19th century, it was only natural for psychologists to borrow some of the techniques of the philosopher. One such technique was introspection. Introspection was a way of studying human nature and t workings of the human mind from within. It was felt that an understanding of mental processes and the way the mind and brain worked could be reached by careful analysis through alone. Thinking about thinking, you might say. The trouble with this introspective approach was that it was a purely subjective exercise. There was no way of checking up on someone's' introspections. Furthermore, one person's introspections need not necessarily be to same as another person's introspections. Who is to decide which introspections are right and which are wrong?
Disillusionment with the subjective approach to psychological research led the likes of Wilhelm Wundt, William James and John Watson to adopt an objective approach and to establish psychology as an empirical, research based discipline in the same vein as the natural sciences. Introspection and subjectivity was abandoned and a scientific approach and objectivity was adopted. The change totally transformed psychology. Instead of examining human nature and the mind from within, psychology now switched from examining human nature and mind from without. In effect, this saw a shift from focusing and relying on subjective experiences to studying overt behaviour.
In the new psychology, a psychological theory or explanation of how the mind or brain worked had to fit the facts of behaviour as derived from systematic observations and measurements. And for a psychological theory to qualify as a scientific theory, it had to be capable of being put to the test, and in principle, of being proved wrong or falsified.. in other words, a truly scientific psychological theory had to provide predictions or hypotheses that could be put to the test, preferably by means of an experiment. It was not much use having a theory which could not be put to the test, because there was not way of establishing whether the theory was true or false. For example, a theory which states that "Dreams are the residue of daytime thoughts", a theory that may well have been derived through introspection or subjective experiences, would be well nigh impossible to test. It may or may not be true, but it is difficult to think of any objective way of determining its truth or falsity. What the new psychology aimed for, and what is aimed for in psychology today, is to formulate theories that can be objectively put toe the test using either observational techniques or, better still, experimental techniques.
Essentially then the scientific approach in psychology is a matter of methodology used to evaluate theories. The methodology must be objective and theories must be testable. But we have placed no limits on the way in which psychological theories are first derived. They may be based on years of exploratory and painstaking research, or a vague hunch, on a bright idea, on a flash of inspiration or revelation that comes to us in a dream. Or while sitting on the loo, or even based on a political or religious viewpoint. It doesn't really matter where the theories come from so long as they give rise to predictions or hypotheses about how variables are related and which can be tested. This then, is the basis of the scientific approach in psychology.