Single-Case Experimental Designs

1. Single-Case Experimental Designs Slides Prepared by Alison L. O’Malley Passer Chapter 12

2. Single-Case Experimental Designs • Researchers systematically examine how an IV influences the behavior of an individual case • Remember Sperry and Gazzaniga’s split-brain patients? It’s only me!

3. Single-Case Experimental Designs:Key Features • Each participant serves as his/her own control or comparison • Treatment phase vs. baseline phase

4. Single-Case Experimental Designs:Key Features • DV measured across multiple trials • Built-in replication • Data examined separately for each participant • Reliance on visual analysis of data

5. Single-Case Experimental Designs:Advantages • Affords systematic understanding of low base rate phenomena • Flexible • Individual differences are examined rather than “averaged out” What distinguishes single-case experimental designs from case studies?

6. Single-Case Experimental Designs • B.F. Skinner employed this research approach in his operant conditioning work • Advocate of experimental analysis of behavior • Human applications include as applied behavior analysis and beyond

7. Single-Case Experimental Designs:ABAB Designs • Sequence of phases in which treatment is either absent or present • Typically (but not necessarily), treatment absent during “A” phase and present during “B” phase • Often called withdrawal or reversal designs as second A phase often entails withdrawal of treatment

8. ABAB Experiment Target behavior

9. ABAB Single-Case Designs • As before, we must consider how potential confounds might threaten a study’s internal validity • What are some advantages of using an ABAB design as opposed to an AB or ABA design?

10. Drawbacks of ABAB Designs • Ethical concerns surrounding withdrawal of treatment that seems to be effective • If target behavior does not revert to baseline levels during a withdrawal phase, it is difficult to draw conclusions • Multiple-baseline designs are more useful if we have reason to believe a target behavior will not revert to baseline levels

11. Multiple Baseline Designs • Behavior measured repeatedly during a baseline period and then during a treatment period • Some sort of replication is conducted • Timing of treatment is varied to rule out alternative explanations • But watch out for contamination!

12. Multiple Baseline Design Across Subjects • Two or more participants exposed to the same treatment • Introduction of treatment is staggered across participants in order to create baseline periods of varying lengths

13. Multiple Baseline Design Across Behaviors • Same treatment applied to two or more behaviors of the same individual • Introduction of treatment is staggered across behaviors in order to create baseline periods of varying lengths • Describe how this approach could be implemented in a study with three players of your favorite sport or musical instrument

14. Multiple Baseline Design Across Settings • Same treatment applied to the same behavior in two or more settings • Introduction of treatment is staggered across settings • How (if at all) do multiple-baseline designs resolve the ethical quandaries associated with ABAB designs?

15. Changing-Criterion Designs • Initial baseline phase followed by a treatment phase • When target behavior reaches a certain threshold, a new performance criterion is set Criterion 1 Criterion 2 …

16. Extending Single-Case Designs • “Case” not limited to an individual • Can be a larger social unit (e.g., business) classroom)

17. Internal Validity of Single-Case Designs • Unlike group within-subjects designs, single-case designs are rarely counterbalanced • What are the implications of this for internal validity?

18. Data Analysis • Primary reliance on visual data analysis • No standard application of statistical tests • Difficult to examine interactions • What would an ideal set of data look like?

19. External Validity • Why are concerns about external validity often raised with respect to single-case experiments? • How can single-case experimenters defend themselves against these claims of limited external validity?

20. Group vs. Single-Case Designs • A classmate maintains that single-case experimental designs are far superior to between- and within-subjects designs because group designs analyze “averaged” responses. • Respond to this argument.