Case Study Method-Research Methodology

THE CASE STUDY METHOD 

Characteristics
• Case studies, intensive descriptions and analyses of individuals, lack the
degree of control found in small-n experimental designs.
• Case studies are a source of hypotheses and ideas about normal and
abnormal behavior.
A case study is an intensive description and analysis of a single individual. Case studies frequently make use of qualitative data, but this is not always the case (e.g., Smith, Harré, & Van Langenhove, 1995). Researchers who use the case study method obtain their data from several sources, including naturalis- tic observation and archival records, interviews, and psychological tests. A clinical case study frequently describes the application and results of a particular treatment. For example, a clinical case study may describe an individual’s symptoms, the methods used to understand and treat the symp- toms, and evidence for the treatment’s effectiveness. Thus, case studies provide a potentially rich source of information about individuals.
Treatment variables in clinical case studies are rarely controlled system- atically. Instead, several treatments may be applied simultaneously, and the psychologist may have little control over extraneous variables (e.g., home and work environments that influence the client’s symptoms). Thus, a fundamental characteristic of case studies is that they often lack a high degree of control. Without control, it is difficult for researchers to make valid inferences about variables that influence the individual’s behavior (including any treatment). Degree of control is one distinguishing feature between the case study method and single- subject experimental designs, with single-subject experimental designs having a higher degree of control (Kazdin, 2002).
The form and content of case studies are extremely varied. Published case studies may be only a few printed pages long or may fill a book. Many as- pects of the case study method make it a unique means of studying behav- ior. It differs from more experimental approaches in terms of its goals, the methods used, and the types of information obtained (Kazdin, 2002). For example, the case study method is often characterized as “exploratory” in nature and a source of hypotheses and ideas about behavior (Bolgar, 1965). Experimental approaches, on the other hand, are frequently viewed as op- portunities to test specific hypotheses. The case study method has sometimes been viewed as antagonistic to more controlled methods of investigation. A more appropriate perspective is suggested by Kazdin (2002), who sees the case study method as interrelated with and complementary to other research meth- ods in psychology.
The case study method offers both advantages and disadvantages to the research psychologist (Bolgar, 1965; Hersen & Barlow, 1976; Kazdin, 2002). Before reviewing its advantages and disadvantages, however, we will illustrate the method with a summary of an actual case study reported by Kirsch (1978). It is important that you read this slightly abbreviated version of a case study carefully because we will review it when discussing the advan- tages and disadvantages of the case study method.
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).
Sources of Ideas About Behavior 
Case studies provide a rich source of infor- mation about individuals and insights into possible causes of people’s be- havior. These insights, when translated into research hypotheses, can then be tested using more controlled research methods. This aspect of the case study method was acknowledged by Kirsch (1978) when discussing the successful psychotherapy with the woman named Susan. He stated that the “conclusions [of this case study] . . . should be viewed as tentative. It is hoped that the utility of [this technique] will be established by more controlled research” (p. 305). The case study method is a natural starting point for a researcher who is entering an area of study about which relatively little is known.
Opportunity for Clinical Innovation
The case study method provides an oppor- tunity “to try out” new therapeutic techniques or to try unique applications of existing techniques. The use of self-management training (SMT) in psychother- apy represents a clinical innovation because Kirsch changed the typical client– therapist relationship. The SMT approach is based on teaching clients to be their own therapists—in other words, to identify problems and design behavioral techniques for dealing with them. The client is both client and therapist, while the therapist acts as supervisor. In a similar vein, Kubany (1997) reported the ef- fect of a “marathon” 1-day cognitive therapy session with a Vietnam War veteran suffering from multiple sources of combat-related guilt. Therapy of this kind gen- erally occurs over many sessions, but the fact that this intensive session appeared to be successful suggests a new way to conduct this type of clinical intervention.
Method to Study Rare Phenomena
Case studies are also useful for studying rare events. Some events appear so infrequently in nature that we can describe them only through the intensive study of single cases. Many of the case studies described in books by Oliver Sacks, for example, describe individuals with rare brain disorders. The study of autistic savants and other individuals with excep- tional memory abilities, which we mentioned at the beginning of this chapter, are also examples of how the case study is used to investigate rare events.

Challenge to Theoretical Assumptions A theory that all Martians have three heads would quickly collapse if a reliable observer spotted a Martian with only two heads. The case study method can often advance scientific thinking by providing a “counterinstance”: a single case that violates a general proposition or
universally accepted principle (Kazdin, 2002). Consider a theory suggesting that the ability to process and produce human speech is to some extent based on our ability to appreciate tonality, especially in such tonally dependent lan- guages as Chinese. The ability to process speech intonations and inflections, as well as the “sing-song” aspect of some speech, would seem to bear a re- semblance to music appreciation. How would such a theory explain normal speech perception and production by someone who cannot hear music? Are there such individuals?
Oliver Sacks (2007) relates several case studies of persons with congenital “amusia,” or the inability to hear music. One individual, for example, was a woman who had never heard music, at least not in the way music is heard by most of us. She could not discriminate between melodies, nor tell if one musi- cal note was higher or lower. When asked what music sounded like to her, she replied that it was like someone throwing pots and pans on the floor. Only in her seventies was her condition diagnosed and she was introduced to others with this unusual neurological disorder. Yet she and others with amusia show normal speech perception and production. Clearly, a theory closely linking lan- guage ability and musical appreciation would need to be modified based on these case studies.
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 acuity).