One has to be careful with "ism" words. They often have both loose meanings and strict meanings. And sometimes multiple meanings of each type. Behaviorism is one of those "isms". Loosely speaking, behaviorism is an attitude -- a way of conceiving of empirical constraints on psychological state attribution. Strictly speaking, behaviorism is a doctrine -- a way of doing psychological science itself.

Wilfred Sellars (191289), the distinguished philosopher, noted that a person may qualify as a behaviorist, loosely or attitudinally speaking, if they insist on confirming hypotheses about psychological events in terms of behavioral criteria (1963, p. 22). A behaviorist, so understood, is someone who demands behavioral evidence for any psychological hypothesis. For such a person, there is no knowable difference between two states of mind (beliefs, desires, etc.) unless there is a demonstrable difference in the behavior associated with each state. Consider the current belief that is is raining. If there is no difference in my behavior between believing that it is raining and currently thinking that the sun is bright, there is no grounds for attributing the one belief to me rather than the other. The attribution is empirically unconstrained.

Arguably, there is nothing truly exciting about behaviorism loosely understood. It enthrones behavioral evidence, an arguably inescapable premise in not just psychological science but in ordinary discourse about mind and behavior. Just how behavioral evidence should be 'enthroned' (especially in science) may be debated. But enthronement itself is not in question.

Not so behaviorism the doctrine. It has been widely and vigorously debated. This entry is about the doctrine, not the attitude. Behaviorism, the doctrine, has caused considerable excitation among both advocates and critics. In a manner of speaking, it is a doctrine, or family of doctrines, about how to enthrone behavior not just in the science of psychology but in the metaphysics of human and animal behavior.

Behaviorism, the doctrine, is committed in its fullest and most complete sense to the truth of the following three sets of claims.

The three sets of claims are logically distinct. Moreover, taken independently, each helps to form a type of behaviorism. Methodological behaviorism is committed to the truth of (1). Psychological behaviorism is committed to the truth of (2). Analytical behaviorism (also known as philosophical or logical behaviorism) is committed to the truth of the sub-statement in (3) that mental terms or concepts can and should be translated into behavioral concepts.

Other nomenclature is sometimes used to classify behaviorisms. Georges Rey (1997, p. 96), for example, classifies behaviorisms as methodological, analytical, and radical, where radical is Rey's term for what I am classifying as psychological behaviorism. I reserve the term radical for the psychological behaviorism of B. F. Skinner. Skinner employs the expression radical behaviorism to describe his brand of behaviorism or his philosophy of behaviorism (see Skinner 1974, p. 18). In the classification scheme used in this entry, radical behaviorism is a sub-type of psychological behaviorism, primarily, although it combines all three types of behaviorism (methodological, analytical, and psychological).

Methodological behaviorism is a normative theory about the scientific conduct of psychology. It claims that psychology should concern itself with the behavior of organisms (human and nonhuman animals). Psychology should not concern itself with mental states or events or with constructing internal information processing accounts of behavior. According to methodological behaviorism, reference to mental states, such as an animal's beliefs or desires, adds nothing to what psychology can and should understand about the sources of behavior. Mental states are private entities which, given the necessary publicity of science, do not form proper objects of empirical study. Methodological behaviorism is a dominant theme in the writings of John Watson (18781958).

Psychological behaviorism is a research program within psychology. It purports to explain human and animal behavior in terms of external physical stimuli, responses, learning histories, and (for certain types of behavior) reinforcements. Psychological behaviorism is present in the work of Ivan Pavlov (18491936), Edward Thorndike (18741949), as well as Watson. Its fullest and most influential expression is B. F. Skinner's work on schedules of reinforcement.

To illustrate, consider a food-deprived rat in an experimental chamber. If a particular movement, such as pressing a lever when a light is on, is followed by the presentation of food, then the likelihood of the rat's pressing the lever when hungry, again, and the light is on, is increased. Such presentations are reinforcements, such lights are (discriminative) stimuli, such lever pressings are responses, and such trials or associations are learning histories.

The rest is here:
Behaviorism (Stanford Encyclopedia of Philosophy)