Single-Case Research Designs ♣

1. Single-Case Research Designs ♣ Chapter 12 Back to Brief Contents • Introduction  • Single-Case Designs • Methodological Considerations in Using Single-Case Designs • Criteria for Evaluation Change • Rival Hypotheses 

2. 12.0 Introduction 1/2 Back to Chapter Contents • Single-case designs—Use only one participant or one group of participants • Research in psychology began with the intensive study of single organisms • Pavlov • Ebbinghaus • Changed with Fisher’s introduction of ANOVA • Skinner continued single-case research • Single-case designs became more acceptable with the growth in research in behavior therapy

3. 12.0 Introduction 2/2 Back to Chapter Contents • Characteristics of single-case designs • Are timeseries designs • Must alter the time-series design to eliminate the history threat • Assessment of a treatment effect is based on the assumption that the pattern of pretreatment responses would continue in the absence of the treatment

4. 12.1 Single-Case Designs 1/9 Back to Chapter Contents • ABA Design • Interaction Design • Multiple-Baseline Design • Changing-Criterion Design

5. 12.1 Single-Case Designs 2/9 Back to Chapter Contents • A-B-A Design Fig 12.1 A B A Baseline Treatment Baseline • Characteristics • Demonstration of the treatment requires a return to baseline Fig 12.2 • A strong treatment effect would reduce changes of a reversal to baseline • To avoid ending on baseline, can extend the design to A-B-A-B design Fig 12.3Fig 12.4

6. 12.1 Single-Case Designs 3/9 Back to Chapter Contents • A-B-A Design Fig 12.1 • Characteristics • Reversal versus withdrawal of treatment • Withdrawal: remove treatment • Reversal: treatment alternative but incompatible behavior • (e.g.) Reversal: reinforcement (praise) B: interaction with other children 2-nd A: interaction with adults

7. 12.1 Single-Case Designs 4/9 Back to Chapter Contents • Interaction DesignFig 12.512.612.712.8 A B A B BC B BC A C A C BC C BC A=baseline, B=treatment, C=treatment and BC=combined treatment • Tests the combined effect of two treatments • Must use both sequences to test the combined influence over the effect of just one variable.

8. 12.1 Single-Case Designs 5/9 Back to Chapter Contents • Interaction DesignFig 12.512.612.712.8 • Disadvantages: • At least two participants required • Only each variable not produce maximum increment

9. 12.1 Single-Case Designs 6/9 Back to Chapter Contents • Multiple-Baseline Design Fig 12.912.10 First person A B B B Second Person A A B B Third Person A A A B A=Baseline and B=Treatment • Treatment effect demonstrated by a change in behavior only when treatment is given • Requires independence of behaviors to demonstrate an effect

10. 12.1 Single-Case Designs 7/9 Back to Chapter Contents • Multiple-Baseline Design Fig 12.912.10 • Advantage: avoid the problem of reversibility • Difficulty: Notinterdependence of behaviors investigated • Recommendations: • Select behaviors as independent as possible • Using different individuals or situations • Correlate the baseline behaviors (low r?) • Independent after implementation of treatment • Use several baselines • Implement a reversal on one of the baseline behavior

11. 12.1 Single-Case Designs 8/9 Back to Chapter Contents • Changing-Criterion Design Fig 12.1112.12 Baseline T1 T2 T3 T4 T1 through T4 represents presentation of the treatment with a different performance criterion

12. 12.1 Single-Case Designs 9/9 Back to Chapter Contents • Changing-Criterion Design Fig 12.1112.12 • Factors to consider in using this design • Length of baseline and treatment—long enough for the behavior to stabilize • Treatment: different length • If treatment: constant length baseline be longer (history, maturation) • Size of criterion change—large enough to notice a change, small enough so that it can be achieved • Number of treatment phases—at least two but enough to demonstrate a treatment effect

13. 12.2 Methodological Considerations in Using Single-Case Designs 1/3 Back to Chapter Contents • Baseline • Changing One Variable at a Time • Length of Phases

14. 12.2 Methodological Considerations in Using Single-Case Designs 2/3 Back to Chapter Contents • Baseline—must be stable to demonstrate a treatment change • What is stable baseline • Absence of trend or in the direction opposite of what is expected from the treatment • Little variability

15. 12.2 Methodological Considerations in Using Single-Case Designs 3/3 Back to Chapter Contents • Change only one variable at a time • 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

16. 12.3 Criteria for Evaluation Change Back to Chapter Contents • Experimental criterion • Replication • Nonoverlap of treatment and baseline phases • Therapeutic criterion • Researchers often use social validation—does it produce a change in the client’s daily functioning? • Social comparison—compare behavior with nondeviant peers • Subjective evaluation—do others who interact with the client see a change?

17. 12.4 Rival Hypotheses Back to Chapter Contents • Nonreversible changes may be due to extraneous variables • Behaviors must be independent to rule out extraneous variables • Instructions • Experimenter expectancies can exist • Sequencing effects can exist