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

2. 12.0 Introduction 1/2 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  Back to Chapter Contents

3. 12.0 Introduction 2/2 Characteristics of single-case designs  Are time series 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  Back to Chapter Contents

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

5. 12.1 Single-Case Designs 2/9 A-B-A Design Fig 12.1 Fig 12.1 A B A Baseline Treatment Baseline  Characteristics Demonstration of the treatment requires a return to baseline Fig 12.2 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 12.3 Fig 12.4 Fig 12.3Fig 12.4  Back to Chapter Contents

6. 12.1 Single-Case Designs 3/9 A-B-A Design Fig 12.1 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  Back to Chapter Contents

7. 12.1 Single-Case Designs 4/9 Interaction Design Fig 12.5 12.6 12.7 12.8 Fig 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.  Back to Chapter Contents

8. 12.1 Single-Case Designs 5/9 Interaction Design Fig 12.5 12.6 12.7 12.8 Fig 12.512.612.712.8  Disadvantages: At least two participants required Only each variable not produce maximum increment  Back to Chapter Contents

9. 12.1 Single-Case Designs 6/9 Multiple-Baseline Design Fig 12.9 12.10 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  Back to Chapter Contents

10. 12.1 Single-Case Designs 7/9 Multiple-Baseline Design Fig 12.9 12.10 Fig 12.912.10  Advantage: avoid the problem of reversibility  Difficulty: Not interdependence 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  Back to Chapter Contents

11. 12.1 Single-Case Designs 8/9 Changing-Criterion Design Fig 12.11 12.12 Fig 12.1112.12 BaselineT 1 T 2 T 3 T 4 T 1 through T 4 represents presentation of the treatment with a different performance criterion  Back to Chapter Contents

12. 12.1 Single-Case Designs 9/9 Changing-Criterion Design Fig 12.11 12.12 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  Back to Chapter Contents

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

14. 12.2 Methodological Considerations in Using Single-Case Designs 2/3 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  Back to Chapter Contents

15. 12.2 Methodological Considerations in Using Single-Case Designs 3/3 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  Back to Chapter Contents

16. 12.3 Criteria for Evaluation Change 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?  Back to Chapter Contents

17. 12.4 Rival Hypotheses 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  Back to Chapter Contents