The primary goal of withdrawal designs is to demonstrate a clear functional relationship between a specific intervention and a target behavior. This means establishing that the observed changes in behavior are directly caused by the application of the intervention.
Understanding the Functional Relationship
In behavioral research, a "functional relationship" implies a cause-and-effect link. When utilizing withdrawal designs, researchers aim to show that the intervention is responsible for the behavior change, and conversely, that the behavior reverts to its previous state (or close to it) when the intervention is removed. This process strengthens the evidence that the intervention, and not some other unrelated factor, is truly effective.
Achieving Experimental Control through A-B-A Designs
The ability to demonstrate this functional relationship is significantly enhanced through the strategic withdrawal of the intervention, which increases experimental control. A common and foundational type of withdrawal design is the A-B-A design, characterized by three distinct phases:
- A (Baseline): This initial phase involves observing and measuring the target behavior before any intervention is introduced. The goal is to establish a stable and consistent pattern of the behavior under natural conditions.
- B (Intervention): In this phase, the specific intervention is applied, and the target behavior continues to be measured. If the intervention is effective, a noticeable change in the behavior should occur.
- A (Withdrawal/Return to Baseline): The crucial third phase involves removing the intervention and returning to the original baseline conditions. If the behavior changes back towards its initial baseline level when the intervention is withdrawn, it provides strong evidence that the intervention was indeed responsible for the changes observed in the "B" phase.
This systematic process of introducing and then removing the intervention allows researchers to rigorously assess its impact.
Phases of a Withdrawal Design
The table below illustrates the typical progression and purpose of each phase in an A-B-A withdrawal design:
| Phase | Description | Purpose |
|---|---|---|
| A (Baseline) | Measurement of target behavior before intervention | To establish a stable, pre-intervention level of the target behavior. |
| B (Intervention) | Introduction of the intervention | To observe how the target behavior changes in the presence of the intervention. |
| A (Withdrawal) | Removal of the intervention, return to baseline | To confirm that the intervention was responsible for the behavior change by observing a reversal back towards baseline levels. |
Why Withdrawal is Crucial
The act of withdrawing the intervention is critical because it helps rule out other potential explanations for the observed behavior change. If the behavior improves during the intervention phase and then deteriorates when the intervention is removed, it strongly suggests a direct causal link. This methodical approach is vital for validating the effectiveness of behavioral interventions and ensuring that strategies are chosen based on robust evidence.
