What does a scientist do when he or she "explains" something？ Scientific explanation comes

in two forms: generalization and reduction. Most psychologists deal with generalization. They explain particular instances of behavior. as examples of general laws. For instance most psychologists would explain a pathologically strong fear of dogs as an example of classical conditioning. Presumably, the person was frightened earlier in life by a dog. An unpleasant stimulus was paired with the sight of the animal (perhaps the person was knocked down by an exuberant dog) and the subsequent sight of dogs evokes the earlier response--fear.

Most physiologists deal with reduction. Phenomena are explained in terms of simpler phenomena. For example, the movement of a muscle is explained in terms of changes in the membrane of muscle cells, entry of particular chemicals, and interactions between protein molecules within these cells. A molecular biologist would "explain" these events in terms of forces that bind various molecules together and cause various parts of these molecules to be attracted to one another.

Like other scientists, physiological psychologists believe that all natural phenomena--including human behavior---are subject to the laws of physics. Thus, the laws of behavior. can be reduced to descriptions of physiological processes.

How does one study the physiology of behavior？ Physiological psychologists cannot simply be reductionists. It is not enough to observe behaviors and correlate them with physiological events that occur at the same time. Identical behaviors, under different conditions, may occur for different reasons, and thus be initiated by different physiological mechanisms. This means that we must understand "psychologically" why a particular behavior. occurs before we can understand what physiological events made it occur.

What does the passage mainly discuss？

A．The difference between "scientific" and "unscientific" explanations.

B．The difference between human and animal behavior.

C．How fear would be explained by the psychologist, physiologist, and molecular biologist.

D．How scientists differ in their approaches to explaining natural phenomena.