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296 PART IV: Applied Research• Ethical considerations may prevent psychologists from using the ABABdesign.• In multiple-baseline designs, a treatment effect is shown when behaviorsin more than one baseline change only following the introduction of atreatment.• Multiple baselines may be observed across individuals, behaviors, orsituations.• Interpreting the causal effect of treatment is difficult in multiple-baselinedesigns when changes are seen in a baseline before an experimentalintervention; this can occur when treatment effects generalize.Key ConceptsThe ABAB Design Researchers use the ABAB design to demonstrate thatbehavior changes systematically when they alternate “no-treatment” and“treatment” conditions. An initial baseline stage (A) is followed by a treatmentstage (B), next by a return to baseline (A), and then by another treatment stage (B).Because treatment is removed during the second A stage, and any improvementin behavior is likely to be reversed at this point, this design is also calleda reversal design. The researcher using the ABAB design observes whether behaviorchanges immediately upon introduction of a treatment variable (first B),whether behavior reverses when treatment is withdrawn (second A), andwhether behavior improves again when treatment is reintroduced (second B). Ifbehavior changes following the introduction and withdrawal of treatment, theresearcher gains considerable evidence that the treatment caused the behaviorchange.Horton (1987) used an ABAB design to assess the effects of facial screeningon the maladaptive behavior of a severely mentally impaired 8-year-old girl.Facial screening is a mildly aversive technique involving the application of aface cover (e.g., a soft cloth) when an undesirable behavior occurs. Previousresearch had shown this technique to be effective in reducing the frequencyof self-injurious behaviors such as face slapping. Horton sought to determinewhether it would reduce the frequency of spoon banging by the young childat mealtime. The spoon banging prevented the girl from dining with her classmatesat the school for exceptional children that she attended. The banging wasdisruptive not only because of the noise but also because it often led her to flingfood on the floor or resulted in her dropping the spoon on the floor.A clear definition of spoon banging was made to distinguish it from normalscooping motions. Then, a paraprofessional was trained to make observationsand to administer the treatment. A frequency count was used to assess themagnitude of spoon banging within each 15-minute eating session. During theinitial, or baseline, period the paraprofessional recorded frequency and, witheach occurrence of the response, said “no bang,” gently grasped the girl’s wrist,and returned her hand to her dish. The procedure was videotaped, and an independentobserver viewed the films and recorded frequency as a reliabilitycheck. Interobserver reliability was approximately 96%. The baseline stage wasconducted for 16 days.The first treatment period began on Day 17 and lasted for 16 days. Eachtime spoon banging was observed, the paraprofessional continued to give the