After studying Chapter 10, you should know and understand the following key points:

The Case Study Method

Characteristics

Case studies, intensive descriptions and analyses of individuals, lack the degree of control found in N = 1 experimental designs.

Case studies are a source of hypotheses and ideas about normal and abnormal behavior.

Advantages of the Case Study Method

Case studies provide new ideas and hypotheses, opportunities to develop new clinical techniques, and a chance to study rare phenomena.

Scientific theories can be challenged when the behavior of a single case contradicts theoretical principles or claims and theories can receive tentative support using evidence from case studies.

Idiographic research (the study of individuals to identify what is unique) complements nomothetic research (the study of groups to identify what is typical).

Disadvantages of the Case Study Method

Researchers are unable to make valid causal inferences using the case study method because extraneous variables are not controlled and several "treatments" may be applied simultaneously in case studies.

Observer bias and biases in data collection can lead to incorrect interpretations of case study outcomes.

Whether results from a case study may be generalized depends on the variability within the population from which the case was selected; some characteristics (e.g., personality) vary more across individuals than others (e.g., visual system).

Thinking Critically About Testimonials Based on a Case Study

• Being mindful of the limitations of the case study method can be helpful when evaluating individuals' testimonials about the effectiveness of a particular treatment.

In applied behavioral analysis, the methods developed within the experimental analysis of behavior are applied to socially relevant problems.

Characteristics of Single-Case (N = 1) Experiments

Researchers manipulate an independent variable in single-case experiments; therefore, these designs allow more rigorous control than case studies.

In single-case experiments, baseline observations are first recorded to describe what an individual's behavior is like (and predicted to be like in the future) without treatment.

Baseline behavior and behavior following the intervention are compared using visual inspection of recorded observations.

Specific Experimental Designs

In the ABAB design, baseline (A) and treatment (B) stages are alternated to determine the effect of treatment on behavior.

Researchers conclude that treatment causes behavior change when behavior changes systematically with the introduction and withdrawal of treatment.

Interpreting the causal effect of the treatment is difficult in the ABAB design if behavior does not reverse to baseline levels when treatment is withdrawn.

Ethical considerations may prevent psychologists from using the ABAB design.

In multiple-baseline designs, a treatment effect is shown when behaviors in more than one baseline change only following the introduction of a treatment.

Multiple baselines may be observed across individuals, behaviors, or situations.

Interpreting the causal effect of treatment is difficult in multiple-baseline designs when changes are seen in a baseline before an experimental intervention; this can occur when treatment effects generalize.

Problems and Limitations Common to all Single-Case Designs

Interpreting the effect of a treatment can be difficult if the baseline stage shows excessive variability or increasing or decreasing trends in behavior.

The problem of low external validity with single-case experiments can be reduced by testing small groups of individuals.

Although psychologists can compare treatment and no-treatment conditions in single-case experiments, they cannot easily examine interactions among variables using this method.