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CHAPTER 9: Single-Case Designs and Small-n Research 297FIGURE 9.3Frequency of spoon-banging responses across baseline, treatment, and follow-up phasesof study. (Adapted from Horton, 1987.)5BaselineFacialScreeningBaselineFacialScreeningFollow-upMovements per Minute1.5.1.050 10 20 30 40 50 60 6 10 15 19SessionsMonthscorrective feedback of “no bang” and returned the girl’s hand to her dish. However,the paraprofessional now also pulled a terry-cloth bib over the girl’s entireface for 5 seconds. Release from facial screening was contingent on the participant’snot banging for 5 seconds. The first treatment phase was followed by asecond baseline period and another treatment phase. Posttreatment observationswere also made at 6, 10, 15, and 19 months.Figure 9.3 shows changes in the frequency of the girl’s spoon-banging behavioras a function of alternating baseline and treatment phases. Facial screeningwas not only effective in reducing this behavior during treatment phases;follow-up observations revealed that the spoon banging was still absentmonths later. Following the final treatment phase, the girl no longer requireddirect supervision during mealtime at either school or home and was permittedto eat with her peers. There was clear evidence that the application of thefacial screening was responsible for eliminating the spoon banging. The facialscreening was the only treatment that was administered, and visual inspectionof Figure 9.3 shows that behavior changed systematically with the introductionand withdrawal of treatment. The facial-screening technique was a successfulprocedure for controlling the maladaptive behavior of the young child whenother, less intrusive procedures had failed.Methodological Issues Associated with ABAB Designs A major methodologicalproblem that sometimes arises in the context of an ABAB procedure can beillustrated by looking again at the results of the Horton (1987) study shown inFigure 9.3. In the second baseline stage, when application of the facial screeningwas withdrawn, spoon banging increased. That is, the improvement observedunder the preceding treatment stage was reversed. What if the spoon-bangingbehavior had remained low even when the treatment was withdrawn? Whatcan the researcher conclude about the effectiveness of the treatment when behaviorin a second baseline stage does not revert to what it was during the