As we noted, a scientific theory is a general principle used to explain observed facts. Such theories are often stated in the form of relationships. For example, the scientist's response to the teacher was essentially a statement of a relationship between learning and rewards. In many sciences, such relationships are described in formal terms, using mathematical expressions. Unfortunately there are few theories in psychology which can be stated with such precision.
Theories serve three important functions.
First, a theory can summarize many observations. The law of gravity, for example, summarizes a considerable number of observations about apples, stones, feathers, and so on, as they fall to the ground. In psychology, the theory of reinforcement is described as the process of strengthening behavior with the use of consequent events. The second function of a theory lies in its value as a predictor. A good theory describes what will happen in certain conditions.