Examination for Professional Practice of Psychology (EPPP) Practice Test

In an ABAB research design, causality is indicated primarily by the observation that the target behavior reverts to its original baseline levels when the treatment is withdrawn. This pattern of change demonstrates a clear relationship between the intervention and the behavior. When the treatment is applied (the second A phase), if there's a noticeable change in behavior, it suggests that the treatment may be effective. Subsequently, when the treatment is withdrawn (the second B phase), if the behavior returns to the original baseline levels, it strengthens the argument that the treatment had a direct effect on the behavior. This systematic pattern of behavior change before, during, and after the intervention supports the conclusion of causal influence, as it shows that the manipulation of the independent variable (the treatment) is responsible for the changes observed in the dependent variable (the target behavior). The other options do not provide the same clarity regarding causality. Changes in behavior must reflect a consistent and reversible effect of treatment to firmly establish a causal relation, which is specifically highlighted by the behavior returning to baseline levels upon withdrawal of treatment.