[bi-heyv-yuh-riz-uh
m] 
| the theory or doctrine that human or animal psychology can be accurately studied only through the examination and analysis of objectively observable and quantifiable behavioral events, in contrast with subjective mental states. |
A theory that psychology is essentially a study of external human behavior rather than internal consciousness and desires. (See B. F. Skinner)
behaviorism be·hav·ior·ism (bĭ-hāv'yə-rĭz'əm)
n.
A school of psychology that confines itself to the study of observable and quantifiable aspects of behavior and excludes subjective phenomena, such as emotions or motives. Also called behavioral psychology.