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Alternating Treatments Design

Alternating treatments design (i.e., multielement design) – the rapid alternation of comparing two or more treatments (i.e., independent variable) while measuring the effects on the target behavior (i.e., dependent variable).

Types of ATD

  1. Single-phase without a no-treatment control condition
  2. Single-phase with two conditions, one of which is a no-treatment control condition
  3. Two-phase design with initial baseline and treatment phase of two or more conditions (one being a no-treatment condition)
  4. Three-phase design with initial baseline and treatment phase of two or more conditions (one being a no-treatment condition) and a final phase of best-treatment-only

The fourth type shows the most functional control.

Advantages

  • Does not require treatment withdrawal
  • Quick comparison of interventions
  • Applicable for behaviors that cannot be reversed (skill acquisition)
  • Minimizes sequence effects
  • Appropriate for data that are unstable
  • Appropriate for addressing effects of generalizing to other behaviors
  • Intervention can begin immediately (no need for baseline)

Disadvantages

  • Multiple treatment interference – While ATD minimizes sequence effects, it can raise questions about multiple treatment interference: confounding effects of one treatment influenced by another treatment administered at the same time.
  • Unnatural rapid alternation – The quick alternations (and quick identification of an appropriate treatment) should outweigh any negative effects.
  • Limited capacity – the maximum of four treatments should be compared at once. When possible, comparing two treatments at a time is best practice.  
  • Selection of treatments – ideally one could compare any treatment but in reality, the treatments should be different enough for the participant to be able to discriminate between the two. This treatment also isn’t appropriate for a procedure that takes a continuous period of implementing.

References

Barlow, D.H., & Hayes, S.C. (1979). Alternating treatments design: One strategy for comparing the effects of two treatments in a single subject. Journal of Applied Behavior Analysis, 12(2), 199-210. doi: 10.1901/jaba.1979.12-199

Cooper J.O, Heron T.E, Heward W.L. Applied behavior analysis (2nd ed.) Upper Saddle River, NJ: Pearson; 2007. [Google Scholar]

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About the Author: Becca Duncan, M.A., BCBA, is a supervisor with the Behavior Analyst Mentorship Network. She has worked in the field since 2012 in residential programs, day programs, schools, in home, and in clinic settings with ages ranging from 2-95-years-old. Becca’s expertise includes ABA therapy, supervision, skill acquisition, children with autism, and adults with complex needs.

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