Experimental Design: Single-Participant Designs/ The Operant Approach

1. Experimental Design: Single-Participant Designs/ The Operant Approach

2. Single Subject Research • Single is a misnomer • Multiple subject most often used • Single relates to the unit of analysis • Involves • Repeated observation of behavior • Manipulation of one or more IVs on a WS basis • Demonstrations of stability within and across levels of IV • Trend and Bounce

3. Operant Phase Baseline Treatment Length of phase Changing phase Measuring the response Concepts in the experimental analysis of behavior

4. Phase • Phase • The period of time during which the individual is studied to see how his or her behavior changes when different treatments are introduced, withdrawn, or changed.

5. Baseline • Baseline phase • The free level of the operant or response is measured. • Need to know how strong the target behavior is before we can assess any changes that might occur in its strength when we introduce a treatment. • Baseline measurements need to be taken for long enough so that we have a good idea of what the operant level is prior to treatment.

6. Treatment • The IV is introduced and the behavior is carefully measured and recorded. • Treatment usually involves some kind of reinforcement of punishment procedure. • Reinforcement procedure – where the operant response is followed by a stimulus (the reinforcer) intended to increase its strength. • Punishment procedure – where the behavior is followed by a stimulus (the punisher) intended to reduce its strength.

7. Length of phase • Length of phase • Depends on the stability of the behavior being observed. • Each phase generally continues until the target behavior is stable or consistent over time.

8. Changing phase • Once we see a consistent level of responding we can introduce, withdraw, or change a treatment. • Goal  to show that our treatment causes a change in the operant level. • Interpretation of the results is more subjective than in multiparticipant research where the statistical analysis provides more objective answers. • Results should be replicable.

9. Measuring the response • Various measures of response strength: • Rate or frequency of responding in a specific period of time. • Cumulative record – total frequency of the operant behavior and the time when the response occurred. • Data often displayed in a cumulative response graph. • Use graphic analysis to determine whether or not the IV had an effect .

10. ABA and ABAB withdrawal designs • A – Baseline phase • B – Treatment phase • Second A – Withdrawal of treatment • ABA design – gather baseline data (A), then introduce a treatment (B), and then withdraw the treatment and measure responding again (A). • Withdrawal of treatment acts as a control and allows us to establish a causal relationship. • ABAB design – includes a second treatment phase (e.g. used in behavior modification).

11. Graphical Presentation

12. Graphical Presentation

13. Multiple baseline design • Multiple baseline designs • Allow us to assess our treatment by comparing its effect on different behaviors, settings, or people rather than by withdrawing treatment. • Advantageof multiple baseline design over withdrawal designs: baseline conditions are not reintroduced after treatment has begun. • Therefore, they are useful for studying treatments that we expect to be permanent or long-lasting.

14. Multiple baseline design • Multiple baseline across participants design • Introduce treatment in two or more individuals. • Multiple baseline across behaviors design • Introduce treatment for more than one behavior. • Multiple baseline across settings design • Measure our targeted behavior in different settings and apply treatment in one setting at a time.

15. Alternating treatment design • Useful for evaluating the effect of more than one treatment on the behavior of an individual within an experiment. • After the baseline phase, different treatments are alternated several times. The order of the treatments is randomly determined or counterbalanced to control carryover effects. • Each treatment effect is replicated each time it is introduced. A treatment may be applied a few times or many times.

16. Changing criterion design • Use when a goal behavior can be quantified into different target levels or steps. • When the behavior reaches the targeted level, the criterion is changed, and the behavior must meet the new criterion. • The final goal behavior is reached in a step-wise fashion.

17. Component-analysis design • This design consists of a series of phases in which each phase adds or subtracts one component of a complex treatment to determine how each component contributes to the overall treatment effectiveness • Example – Studying reward and punishment for biting behavior in an autistic boy BC-B-BC-C-BC BC – combination of the reward and punishment B – reward only C – punishment only

18. Advantages and disadvantages of single participant designs • Single participant designs are particularly well suited in clinical settings as causal links can be established. This can also be a disadvantage as a treatment that works for one individual may not work for others, in which case the study lacks external validity. • Conditions can be tailored to the individual being studied rather than standardized for a group. The researcher can easily modify the design even after the study has begun without jeopardizing its integrity.

19. Advantages and disadvantages of single participant designs • Using response rate as the primary DV can be a disadvantage because other measures of behavior (e.g.. number correct, reaction time, rating, etc.) are excluded. • Single participant designs use a seemingly more subjective approach that relies on the experience and integrity of the researcher. This can be seen as both a strength and a weakness.

20. Advantages and disadvantages of single participant designs • The single participant approach can be viewed as offering the best of both worlds to clinicians  treatment can be provided at the same time that cause and effect is demonstrated. This meshing of experimental research and clinical practice is perhaps the biggest strength of single participant designs.