The Paradigm of Functionalism
The Subject Matter of Psychology: Psychology is the study of mental activity (e.g.. perception, memory, imagination, feeling, judgment). Mental activity is to be evaluated in terms of how it serves the organism in adapting to its environment.
The Methods of Psychology: Mental acts can be studied through introspection, the use of instruments to record and measure, and objective manifestations of the mind, through the study of its creation and products, and through the study of anatomy and physiology.
The functionalists tended to use the term "function" rather than loosely. The term is used in at least two different ways. It can refer to the study of how a mental process operates. This is a major departure from the study of the structure of a mental process, the difference between stopping a train to tear it apart to study its parts (structuralism), and looking at how the systems interact while it is running (functionalism). The term "function" can also refer to how the mental process functions in the evolution of the species, what adaptive property it provides that would cause it to be selected through evolution.
Functionalism never really died, it became part of the mainstream of psychology. The importance of looking at the process rather than structure is a common attribute of modern psychology. As an individual approach it lacked a clear formulation and inherited the problems of structuralist reliance on introspection.