Professor Leanne Togher
Discipline of Speech Pathology, The University of Sydney
There are many ways to introduce experimental control to a single case study design.
One way to introduce experimental control is by introducing a reversal design (ABA design).
Repeat baseline and intervention phases. If the behaviour goes up and down in response to the change from baseline to intervention conditions (i.e., no intervention to intervention), than we can have confidence that it is the intervention that is leading to the change in behaviour.
Useful for behaviours that are heavily dependent on intervention, where learning is not expected.
However, two key limitations of reversal designs are:
- If we are attempting to increase or decrease a potentially harmful behaviour (e.g., head banging), withdrawing treatment and then re-introducing it to establish experimental control would likely be unethical.
- If learning is expected to occur, than we would not expect the behaviour to return to baseline levels following the removal of the intervention. In this case, a multiple baseline design is often more appropriate (discussed next).
Think about the goals you routinely target when working with clients in your clinical practice. Identify 3 goals for which measurement using a reversal design could be appropriate.
Next, identify 3 goals for which measurement using a reversal design would be impractical or inappropriate, and explain why.