Single subject designs are thought to be a direct result of the research of B.F. Skinner who applied the techniques of operant conditioning to subjects and measured the outcomes at various points in time. Because of this, single subject designs are often considered the design of choice when measuring behavioral change or when performing behavioral modification. Rather than comparing groups of subjects, this design relies on the comparison of treatment effects on a single subject or group of single subjects.
An important aspect of this type of study is the gathering of pretest information, often called a baseline measure. It is important to measure the dependent variable or behavior prior to administering any treatment. Without this information, it is difficult, and likely impossible to determine if any change has occurred. Also often associated with this design are periods of measurement to determine not only a change but the degree of change through the process of behavioral modification. We’ll look at the two most common applications of this design, including the A-B-A-B design and Multiple Baselines.