Abstract
Recent developments in research on behavioral variability have brought forth new technologies for controlling variable behavior with reinforcement schedules; these new technologies can also be applied to shaping procedures. Through the new technologies, it has been demonstrated that human sensitivity to schedules is closely related to variability in interresponse time. The present article discusses 2 issues related to these findings: (1)a problem in the causal relation between behavioral variability and schedule sensitivity, and (2)when variables have had some effect on human performance, the possibility that some variable such as instruction or reinforcement history has resulted in a change in the variability of the behavior, and that this, in turn, has directly changed the performance. The relationship between behavioral variability and schedule sensitivity indicates the importance of the viewpoint of variation and selection in human behavior. Recent examination of selection theory has expanded its subject to life phenomena broadly, not only biological evolution and operant conditioning, but also other phenomena such as the development of the immune system and neurons. Research on human behavioral variability will progress if it adopts the viewpoint of universal selection theory.
