D-3: IDENTIFY DEFINING FEATURES OF SINGLE-SUBJECT EXPERIMENTAL DESIGNS (E.G., INDIVIDUALS SERVE AS THEIR OWN CONTROLS, REPEATED MEASURES, PREDICTION, VERIFICATION, REPLICATION)©
Single-Subject Experimental Design
In a single-subject experimental design, the baseline data is used to demonstrate changes in a target behavior or dependent variable due to manipulation of the independent variable (Cooper, Heron, and Heward, 2007).
Examples: A-B design, A-B-A-B design, multiple baseline design, alternating treatments design, and changing criterion design
A-B design : Baseline condition (A) and treatment condition (B). Does not show experimental control.
A-B-A-B (baseline, IV, baseline again, IV again) § Preferred because we reintroduce the B condition which enables the replication of treatment effects, which strengthens the demonstration of experimental control
multiple baseline design :
- Presentation of multiple baselines in order to be an alternative to reversal designs
- Allow practitioners to analyze the effects of an independent variable across multiple behaviors, participants or settings without having to withdraw the treatment variable to 20 verify that the improvements in behavior are a direct result of the application of the treatment.
- Verification is established when you add a baseline, and replication is established when the results are replicated with another individual/setting/or behavior.
- 3 to 5 tiers are most common
- Introduction of the IV is always done after a stable baseline
Advantages of multiple baselines:
1. Does not require withdrawing treatment
2. Good for evaluation of progressive, multiple behavior changes sought by many practitioners
Limitations of multiple baseline designs
1. May not allow for a demonstration of experimental control even though a functional relation exists between the IV(independent variable) and the DV(dependent variable)
2. Weaker method for showing experimental control 21
3. Provides more information about the effectiveness of the treatment variable than it does about the function of any particular target behavior
alternating treatments design
Changing criterion Design
- Can be used to evaluate the effects of a treatment that is applied in a graduated or stepwise fashion to a single target behavior
- Requires initial baseline observations on a single target behavior
- Then it is followed by implementation of a treatment program in each of a series of treatment phases
- Each treatment phase is associated with a step-wise change in criterion rate for the target behavior
- Each phase of the design serves as a baseline for the following phase
- Requires careful manipulation of three factors § Length of phases
• Requires stable responding § Magnitude of criterion changes
• There must be a change in level § Number of criterion changes
• The more the better the experimental control
Control(s)
In single-subject designs, each participant serves as their own control. This means that the effects of each condition are compared to the participant's own data (Cooper, Heron, and Heward, 2007).
Example: Participants in a study are working to increase their running distance over time. The researchers use a changing criterion design. They first take baseline data on the participants and then gradually increase the required distance for runners to receive reinforcement in stepwise phases over the course of the study.
Runners could serve as their own controls in a changing criterion design.
Repeated Measures
In single-subject designs, each participant's target behavior or dependent variable is measured in every condition of the study which results in repeated measures (Cooper, Heron, and Heward, 2007).
Example: Even in the most simple of single-subject research designs, an A-B design, the dependent variable is still measured twice: Once in the baseline phase, once in the intervention phase.
Single-subject research designs utilize repeated measures.
Prediction
Prediction is the hypothesis regarding what the outcome of a measurement will be in a study (Cooper, Heron, and Heward, 2007). Also, can the researchers determine what will happen to the dependent variable based on effects from previous phases due to the manipulation of independent variable?
Verification
Verification involves demonstrating that baseline data of the dependent variable would have remained consistent if the independent variable had not been manipulated (Cooper, Heron, and Heward, 2007).
Replication
Replication involves demonstrating similar results in an additional phase (or phases) when repeating the manipulation of the independent variable (Cooper, Heron, and Heward, 2007).
Leave us a comment with a link to a research study that utilizes single-subject research!