Historically, most single-subject designs were developed by behaviorists examining operant conditioning.
The behavior of a single subject (usually a laboratory rat) was observed, and changes in behavior were noted while the researcher manipulated the stimulus or reinforcement conditions.
Although clinicians have adopted the designs, their application is still largely behav- ioral, especially in the field of applied behavior analysis (previously called behavior modification). Despite this strong association with behaviorism, however, single-subject research is not tied directly to any single theoretical perspective and is available as a research tool for general application.