ABA Designs

ABA designs, also known as reversal designs, are among a family of single-case experimental designs most often used by behavioral scientists and educators to evaluate the effectiveness of clinical or educational interventions. This entry first describes ABA designs and provides an example, then discusses phase changes in ABA designs, how ABA designs are used to identify treatment effects, and the limitations of ABA designs.

In a typical ABA design, a relevant dependent variable, such as frequency of tantrums, self-injurious behaviors, or correct academic responses, is measured continuously over some period of time for a single participant. Observation and measurement of this behavior initially occurs under a baseline condition (A in the ABA sequence), in which no independent variable, or treatment, is presented. During this baseline condition, the behavior of interest is assumed to be occurring at its natural level, prior to introduction of the independent variable. After this behavior has demonstrated stability, showing no discernible upward or downward trend during baseline, the treatment or intervention phase (B) is introduced, and measurement of the dependent variable continues. Finally, a return to baseline (A) is programmed,

allowing for assessment of the dependent variable once again in the absence of treatment.

The ABA design can be seen as a formalization of the common “before and after” observations that many of us make of ourselves in response to changes in diet, exercise routines, and other efforts at self-improvement. Such designs are common experimental methods in the natural sciences and were advocated by Claude Bernard, the father of experimental medicine. The general logic of single case experimentation was adopted by psychologist B. F. Skinner as a powerful method for the continuous analysis of learning processes in real time. Beginning in the late 1930s, Skinner pioneered a branch of natural science he called the experimental analysis of behavior, whose products include the contemporary profession of applied behavior analysis.

Applied behavior analysts have been longtime proponents and practitioners of ABA designs, as their work involves the application of basic [Page 4]learning principles to socially significant behavior across many domains, including schools, workplaces, and the home. Behavior analysts utilize single-case ABA designs in order to evaluate the effectiveness of treatments, especially in the area of autism and developmental disabilities. ABA designs are experimental designs that support causal inferences, and the data produced by such designs contribute to our knowledge of evidence-based interventions in the behavioral sciences.

A hallmark of the ABA design is its focus on the behavior of the individual. Behavior analysts consider single-case designs and continuous measurement superior to large-scale group designs in resolving the nuances of moment-to-moment behavior–environment interactions that are often the target of such interventions. Behavior often responds both quickly and dramatically to changes in environmental variables, and the ABA design is a powerful method for assessing these changes. In fact, use of ABA designs can often identify environmental events that correspond to changes in behavior with as much regularity as the lights turn off and on in a room with each flip of a light switch. Each change in condition, from baseline to treatment, or from treatment to baseline, becomes an opportunity to observe a functional relationship between the treatment and the behavioral variable. In addition, further phase changes can be programmed to replicate this functional relationship; thus, ABA designs have intraparticipant replication built into them, and this is an extremely important criterion for developing evidence-based practices.

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