In psychology, mentalism is an umbrella term that refers to those branches of study that concentrate on perception and thought processes: for example, mental imagery, consciousness and cognition, as in cognitive psychology. The term mentalism has been used primarily by behaviorists who believe that scientific psychology should focus on the structure of causal relationships to conditioned responses, or on the functions of behavior.
Neither mentalism nor behaviorism are mutually exclusive fields; elements of one can be seen in the other, perhaps more so in modern times compared to the advent of psychology over a century ago.:11-12, 184
Psychologist Allan Paivio used the term classical mentalism to refer to the introspective psychologies of Edward Titchener and William James.:263 Despite Titchener being concerned with structure and James with function, both agreed that consciousness was the subject matter of psychology, making psychology an inherently subjective field.:263
Concurrently thriving alongside mentalism since the inception of psychology was the functional perspective of behaviorism. However, it was not until 1913, when psychologist John B. Watson published his article "Psychology as the Behaviorist Views It" that behaviorism began to have a dominant influence.:267 Watson's ideas sparked what some have called a paradigm shift in American psychology, leading to the objective and experimental study of human behavior, rather than subjective, introspective study of human consciousness. Behaviorists considered that the study of consciousness was impossible to do, and that the focus on it to that point had only been a hindrance to the field reaching its full potential. For a time, behaviorism would go on to be the dominant force driving psychological thought, advanced by the work of other luminaries such as Ivan Pavlov, Edward Thorndike, and B.F. Skinner.
A scathing review of B.F. Skinner's book Verbal Behavior by Noam Chomsky in 1959 heralded a shift back to a focus on the mental in psychology with the beginning of the cognitive revolution. Critical to the successful revival of the mind or consciousness as a primary focus of study in psychology (and in related fields such as cognitive neuroscience) were technological and methodological advances, which eventually allowed for brain mapping, among other new techniques. These advances provided an objectively experimental way to begin to study perception and consciousness, effectively nullifying the main criticism of mentalism half a century earlier.
However, the cognitive revolution did not kill behaviorism as a research program; in fact, research on operant conditioning actually grew at a rapid pace during the cognitive revolution. In 1994, scholar Terry L. Smith surveyed the history of radical behaviorism and concluded that "even though radical behaviorism may have been a failure, the operant program of research has been a success. Furthermore, operant psychology and cognitive psychology complement one another, each having its own domain within which it contributes something valuable to, but beyond the reach of, the other.":xii
The stimulus-response (S-R) psychology of Watson (1913) is ultimately about behavior and is definitely mechanistic. The behavior-analytic approach of Skinner (1938, 1953) is not ultimately about behavior, and it is definitely not mechanistic. As operant psychologists, we are not concerned with identifying stimuli and responses that bear some fixed relationship to one another and that can be used as building blocks to explain complex behavior patterns. As operant psychologists, we are concerned, first and foremost, with the functions of behavior or, in lay terms, with purpose (Lee, 1988; Morris, 1993; Skinner, 1974), even though we do not analyze and use the term purpose as a lay person would. [...] Functionalism would have been a better term for what we are about but, unfortunately, that term has already been used to describe a school of psychology quite different from ours.
In that sense, the behaviorists were right: as a method, introspection provides a shaky ground for a science of psychology, because no amount of introspection will tell us how the mind works. However, as a measure, introspection still constitutes the perfect, indeed the only, platform on which to build a science of consciousness, because it supplies a crucial half of the equation--namely, how subjects feel about some experience (however wrong they are about the ground truth). To attain a scientific understanding of consciousness, we cognitive neuroscientists "just" have to determine the other half of the equation: Which objective neurobiological events systematically underlie a person's subjective experience?