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Case Study Methodologies

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Research procedures that focuses on a particular individual or group.

A case study (or case history) consists of an intensive, detailed description and analysis of a particular individual, group, or event. Information may be obtained by means of careful observation, interviews, psychological tests, or archival records. Case study research is useful when the researcher is starting to investigate a new area in which there is little information available. Case studies are a rich source of ideas and hypotheses for future research. They can also be used to disconfirm a generally accepted principle. For example, the motor theory of speech perception was based on the claim that decoding and interpreting speech was dependent on the listener's ability to produce speech. In other words, an inability to speak should be accompanied by an inability to comprehend speech. In 1962, Eric Lenneberg reported the outcome of extensive tests over a five-year period on a young boy who was totally inarticulate because of an inborn defect of his vocal tract. Testing showed that he had normal and complete understanding of spoken language. This single counterexample was sufficient to invalidate the theory's basic assumption.

Another widely cited case study is that of Phineas Gage. He was a railway construction foreman who suffered a bizarre accident in 1848 when a three-foot-long iron rod was driven into his skull. The inch-thick rod entered beneath his left eye and exited through the top of his head, destroying much of the prefrontal cortex. Because Gage survived, it provided an opportunity to investigate the effects of brain damage on outward behavior. Although he could still speak and move normally, his friends reported a big change in his personality. The accident transformed him from an amiable, dependable worker into an inconsiderate, foul-mouthed lout. This case, and others like it, suggest that parts of the frontal lobes control social judgment, decision-making, and goal-setting.

While findings from case studies can be valuable, the method has limitations. One major weakness is poor representativeness. Because of the exclusive focus on a particular individual or group, the researcher has no way of knowing whether that individual is typical of people in general. Does the case of Phineas Gage tell us how everyone with a similar injury might be affected? The answer is no, because no two people could ever suffer from precisely identical injuries. Definitive statements about the relationship between brain damage and behavior can only be obtained by means of controlled investigative procedures. Moreover, case studies, by their very nature, do not permit the researcher to draw any conclusions as to causality. In a conventional experiment, the researcher usually has one or more specific hypotheses that are tested by the controlled manipulation of the specific variables of interest. Case studies do not permit careful control, thus it is impossible to identify a specific causal association.

The difficulty of drawing causal inferences from individual case studies is further illustrated by the case of Genie. Genie was a 13-year-old girl who had been grievously neglected by her parents for most of her childhood. From the age of 18 months she was confined to a small room and denied any opportunity for social interactions or normal human contact. No one spoke to her, and she was punished for making any sounds herself. This sad case permitted researchers to test the hypothesis that there is a critical period of language acquisition. The critical period hypothesis maintained that a child's ability to learn its native language effectively ends at the onset of puberty. Genie was 13 when she was rescued. Of particular interest to scientists interested in language learning was the fact that she could not speak. Her only sounds were high-pitched whimpers. Placed in a nurturing environment, would Genie learn to speak? If so, the critical period hypothesis would be refuted. After several years, Genie was able to use words to convey some of her needs, but her grammar and pronunciation remained abnormal and impoverished. While this case is supportive of the critical period hypothesis, crucial information is missing from the picture. We cannot know if Genie was born with mental deficits that might have prevented normal language development, even in the absence of her social isolation.

Because of their very narrow focus, case studies can sometimes be very misleading. John was a normal baby whose penis was burned beyond repair due to a surgical accident in 1963. His doctors persuaded John's parents to have him undergo sex reassignment. At the age of seventeen months, John became "Joan," and from then on the child was treated as a girl. When Joan was evaluated eight years later, the reassignment was judged a success. The case received widespread publicity in textbooks and the mass media. The John/Joan story was heralded as an important demonstration of the influence of social factors in determining gender identity. By age 14, however, Joan suspected that she was a boy. Increasingly dissatisfied with her plight, she became depressed and suicidal. Eventually, Joan underwent plastic surgery and was given male hormone treatments. Today, John is married and reasonably well adjusted. This case clearly illustrates the importance of constitutional factors in establishing gender identity. It also shows us how risky it is to make sweeping generalizations based on observations of a single individual.

Timothy E. Moore

Further Reading

Christensen, L. Experimental methodology. Boston: Allyn & Bacon, 1997.

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