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What Is SSED?
SSED studies are experimental research protocols used by researchers to evaluate the effectiveness of an intervention. It is a common research protocol used in applied behavior analysis therapy.
To help imagine how an SSED study might work, let's imagine we are researchers investigating a new type of intervention we will call “intervention X.” We hypothesize that intervention X will increase the number of correct responses by a child, but we need data to support this. We want to design an experiment to find out how intervention X will affect the number of correct responses given.
In SSED, the subject in the study acts as their own control. This means the effect of the intervention will be compared to the performance of the same person before the intervention.
In SSED designs, “A” and “B” refer to the different stages of the model.
“A” is the baseline. In this stage, the researcher will take measurements without any intervention.
In our experiment, we will count the number of correct responses before we use intervention X. Usually, at least three measurements are taken for the first baseline measurement.
“B” is the treatment phase. In this stage, the researcher will take measurements during the intervention, or treatment.
In our experiment, we will take measurements while using intervention X.
ABA Design
ABA-design studies are sometimes referred to as a withdrawal design. In these studies, the initial behavior is affected by the intervention, then the intervention is withdrawn to see if the behavior returns to the baseline level or is changed.
In our imaginary experiment, an ABA-design study will include:
A—Baseline measurements of correct responses
B—Measurement of correct responses during intervention X
A—Baseline measurements of correct responses after intervention X is removed
Measuring the number of correct responses after intervention X is withdrawn provides another opportunity to show the effect of intervention X.
ABAB Design
In an ABAB-design study, the intervention is reintroduced after a return to the baseline to see how strong the intervention was. The ABAB design is also known as a time-series design or reversal design.
In our imaginary experiment, an ABAB-design study will include:
A—Baseline measurements of correct responses
B—Measurement of correct responses during intervention X
A—Baseline measurements of correct responses after intervention X is removed
B—Measurement of correct responses after intervention X is reintroduced
Reintroducing intervention X has the benefit of providing another experimental control in the study. Many researchers prefer this design because it ends the experiment with treatment instead of an absence of an intervention.
When Are ABAB Designs Used?
Randomized controlled trials are the gold standard for determining effectiveness. However, there are situations where a randomized controlled trial is not feasible or appropriate.
If researchers want to study the effect of an intervention in a classroom setting, a randomized controlled trial is not possible because all students in the classroom will be exposed to the intervention.
There are situations where it is unethical to give two groups of children unequal treatment as would be required in a randomized controlled trial.
In some cases, an ABAB-design study may be able to show the real-world effect of an intervention better than a randomized controlled trial where conditions have to be carefully controlled.
ABAB-design studies can take multiple measurements using a smaller number of subjects than a randomized controlled trial requires. Therefore, these studies will cost much less than large-scale trials. ABAB-design studies are a good way to complete an initial investigation before a large-scale trial is completed.
ABAB Design in Applied Behavior Analysis
ABAB designs can be used to examine several behaviors relevant to applied behavior analysis.
ABAB-design studies have been used to measure the effectiveness of interventions such as response to a verbal elicitation protocol.
A study by Tincani, Crozier, and Alazetta (2006) published in the Journal of Applied Behavior Analysis used an ABAB design to study the effect of positive reinforcement in a Picture Exchange Communication System (PECS) on vocalizations in school-age children with autism. They showed a significant increase in vocalizations using positive reinforcement using the ABAB design.
Disadvantages of ABAB-Design Studies
An ABAB research design is not ideal in experiments where there is no effect on a behavior after an intervention. Because there are not many people in the study, it is hard to determine why there was no effect. In a randomized controlled trial, the lack of effect would be supported by similar effects in many more people.
There may also be an ethical problem with discovering a successful intervention and then withdrawing its use from a child who was benefiting from it. This could be especially problematic when studying behaviors that can cause injury.
Conclusion
Evidence-based treatments are an important part of applied behavior analysis therapies. ABAB research designs are one method to show the effectiveness of different therapies.
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