Chapter 12: Single-Case Research Designs This multimedia product and its contents are protected under copyright law. The following are prohibited by law: Any public performance or display, including transmission of any image over a network; Any public performance or display, including transmission of any image over a network; Preparation of any derivative work, including the extraction, in whole or in part, of any images; Preparation of any derivative work, including the extraction, in whole or in part, of any images; Any rental, lease, or lending of the program Any rental, lease, or lending of the program

Introduction Single-case designs--Use only one participant or one group of participants Single-case designs--Use only one participant or one group of participants Research in psychology began with the intensive study of single organisms Research in psychology began with the intensive study of single organisms – Pavlov –Ebbinghaus –Fisher’s introduction of ANOVA –Skinner continued single-case research –Single-case designs became more acceptable with the growth in research in behavior therapy

Characteristics of Single-Case Designs –Are time series designs But time-series design do not eliminate the history threat—so they must be altered But time-series design do not eliminate the history threat—so they must be altered –Assessment of a treatment effect is based on the assumption that the pattern of pretreatment responses would continue in the absence of the treatment

Single-Case Designs A-B-A Design— A-B-A Design— A B A A B A Baseline Treatment Baseline Baseline Treatment Baseline Baseline-behavior in the absence of any treatment Baseline-behavior in the absence of any treatment Treatment-administration of the IV Treatment-administration of the IV

Characteristics of the ABA Design –Demonstration of the treatment requires a return to baseline –A strong treatment effect could reduce chance of a return to baseline –To avoid ending on baseline can extend the design to A-B-A-B design –There is a difference between a reversal and a withdrawal of treatment

Interaction Design Tests the combined effect of two treatments Tests the combined effect of two treatments Design sequence Design sequence –A BABBCBBC –A C ACBCCBC –A=baseline, B=treatment, C=treatment and BC=combined treatment Must use both sequences to test the combined influence over the effect of just one variable. Must use both sequences to test the combined influence over the effect of just one variable. Disadvantage—interaction effect can be demonstrated only if each variable does not cause a maximum increment in performance Disadvantage—interaction effect can be demonstrated only if each variable does not cause a maximum increment in performance

Multiple-Baseline Design First personABBB First personABBB Second PersonAABB Second PersonAABB Third PersonA AA B Third PersonA AA B A=Baseline and B=Treatment A=Baseline and B=Treatment Treatment effect demonstrated by a change in behavior only when treatment is given Treatment effect demonstrated by a change in behavior only when treatment is given Requires independence of behaviors to demonstrate an effect Requires independence of behaviors to demonstrate an effect

Changing-Criterion Design BaselineT 1 T 2 T 3 T 4 BaselineT 1 T 2 T 3 T 4 T 1 through T 4 represents presentation of the treatment with a different performance criterion T 1 through T 4 represents presentation of the treatment with a different performance criterion Factors to consider in using this design Factors to consider in using this design –Length of treatment—long enough for the behavior to stabilize –Size of criterion change-large enough to notice a change –Number of treatment phases—at least two but enough to demonstrate a treatment effect

Methodological Issues Baseline—must be stable Baseline—must be stable What is stable baseline What is stable baseline Absence of trend or in the direction opposite of what is expected from the treatment Absence of trend or in the direction opposite of what is expected from the treatment Little variability Little variability Change only one variable at a time Change only one variable at a time Length of phases—few guidelines to follow and need to consider the following Length of phases—few guidelines to follow and need to consider the following –Possibility of extraneous variables creeping in with long phases –Carry-over effect—may require short phases –Cyclic variations—maybe need to incorporate the cycle in all phases

Criteria for Evaluating Change Criteria for Evaluating Change Experimental criterion Experimental criterion –Replication –Nonoverlap of treatment and baseline phases Therapeutic criterion—clinical significance Therapeutic criterion—clinical significance –Researchers often use social validation—does it produce a change in the client’s daily functioning Social comparison—compare behavior with nondeviant peers Social comparison—compare behavior with nondeviant peers Subject evaluation—do others who interact with the client see a change Subject evaluation—do others who interact with the client see a change