ABAB Design — Reversal / Withdrawal Design
ABAB Reversal Design · Also known as: reversal design, withdrawal design, ABAB reversal, operant reversal design
The ABAB design is a single-subject experimental methodology that establishes causal control by repeatedly introducing and removing an intervention. A baseline phase (A) is followed by an intervention phase (B), then a return to baseline (A), and a second intervention phase (B), allowing the researcher to demonstrate that observed behavior changes are produced by the intervention rather than by coincidental factors.
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When to use it
Use the ABAB design when (1) you want to demonstrate a causal relationship between a specific intervention and a behavior for an individual participant, (2) the target behavior is expected to reverse when the intervention is removed (i.e., the behavior has not been permanently learned), and (3) repeated measurement of the same outcome variable across all phases is feasible. It is particularly well-suited to applied behavior analysis, special education, clinical psychology, and rehabilitation research. Do NOT use it when the target behavior is unlikely to reverse (e.g., an acquired skill such as reading a word), when the intervention cannot ethically be withdrawn (e.g., life-sustaining treatment or crisis intervention), or when the research question concerns group-level generalization rather than individual-level functional control.
Strengths & limitations
- Provides a strong within-subject demonstration of a causal (functional) relationship without requiring a control group.
- Requires only one participant or a small number of participants, making it feasible when large samples are unavailable.
- The double replication across two A–B pairs substantially strengthens internal validity compared to simpler AB or ABA designs.
- Repeated measurement yields a dense, longitudinal data record that captures the dynamic of behavior change over time.
- Visual analysis methods are transparent and widely understood in behavioral and clinical research communities.
- External validity is limited: findings describe one individual and may not generalize to other participants, settings, or behaviors without systematic replication across cases.
- Requires that the target behavior reverses when the intervention is withdrawn; non-reversible behaviors (skills, habits) are unsuitable.
- Withdrawing an effective intervention raises ethical concerns when participants depend on the treatment for well-being or safety.
- Carryover and history effects can prevent a clean return to baseline, complicating causal interpretation.
- Phase length and the number of data points needed for stability are judgment calls that introduce researcher discretion.
Frequently asked
How is the ABAB design different from the ABA design?
Both are reversal designs, but the ABAB design adds a second intervention phase after the withdrawal. This second B phase provides an independent replication of the functional relationship within the same study, substantially strengthening causal inference. The ABA design ends with the withdrawal phase, leaving the participant in the no-treatment condition and offering only one demonstration of experimental control.
What should I do if behavior does not reverse during the withdrawal phase?
A failure to reverse can mean several things: the behavior may have been permanently acquired (making reversal design inappropriate), a history or carryover effect may be masking the reversal, or the baseline was not stable enough to detect change. Document the non-reversal carefully. If reversal is conceptually expected but does not occur, consider switching to a multiple baseline design, which does not require withdrawal, for future work.
Is it ethical to withdraw a working intervention?
This is a genuine concern. Ethics committees and participants must be informed in advance that the intervention will be temporarily withdrawn. The withdrawal is generally acceptable when (a) the behavior poses no immediate safety risk, (b) the withdrawal phase is kept as brief as scientifically necessary, and (c) the intervention is fully reinstated in the final B phase. Some behaviors — crisis-level self-injury, life-sustaining treatments — make any withdrawal unacceptable, and an alternative design such as a multiple baseline should be used.
How many data points per phase are required?
There is no fixed rule, but the conventional minimum is three data points per phase. In practice, researchers continue collecting data until the series shows a stable pattern — consistent level, predictable trend, and low variability. Five or more data points per phase is a widely recommended target. Stability criteria should be defined a priori to prevent selective stopping.
Can the ABAB design be used with more than one participant?
Yes. Running the ABAB design across multiple participants independently constitutes systematic direct replication, which is how single-subject research builds generalizable evidence. Each participant's data are analyzed individually; the cross-participant consistency of effects is then evaluated as evidence of external validity. This is different from averaging data across participants, which would obscure the individual-level functional relationships the design is built to reveal.
Sources
- Sidman, M. (1960). Tactics of Scientific Research: Evaluating Experimental Data in Psychology. Basic Books. link ↗
- Baer, D. M., Wolf, M. M., & Risley, T. R. (1968). Some current dimensions of applied behavior analysis. Journal of Applied Behavior Analysis, 1(1), 91–97. DOI: 10.1901/jaba.1968.1-91 ↗
How to cite this page
ScholarGate. (2026, June 3). ABAB Reversal Design. ScholarGate. https://scholargate.app/en/experimental-design/abab-design
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- AB DesignExperimental design↔ compare
- ABA DesignExperimental design↔ compare
- Alternating Treatments DesignDisability Studies↔ compare
- Changing Criterion DesignDisability Studies↔ compare
- Multiple Baseline DesignExperimental design↔ compare
- Single-Subject Experimental DesignExperimental design↔ compare