Case studies have been especially useful for: 
- Descriptions of rare or unusual phenomena 
- Assessing, or treating patients with these phenomena 
- Disconfirming “universally" known or accepted information
- Generating testable hypotheses 


Saint Louis University

A case study is an observational research method involving an in-depth, and often longitudinal, examination of an individual, social unit, or event. In psychology, case studies typically provide a detailed qualitative description and analysis of a single individual, frequently one who has a rare condition, unusual disorder, or specific brain damage. While they primarily rely on qualitative tools like interviews and naturalistic observation, case studies can also incorporate quantitative data such as psychological testing or physiological measurements.

Case Study

Trull , T. J., &amp; Prinstein , M. J. (2013). Research Methods in Clinical Psychology . In Clinical Psychology (Eighth, pp. 93–124). Textbook, Wadsworth Cengage Learning . 

Clinical Psychology Eighth Edition 

It's difficult for case studies to generalize universal principles for everyone.

Disadvantages of Case Studies

Purpose of Case Studies 

A primary strength of the case study method is its effectiveness in providing a deep and comprehensive understanding of individuals who are exceptional or unique in some way. The detailed focus allows for insights that are often not possible through research methods designed for larger groups.

Advantage of Case Studies: Understanding Exceptional Individuals

A significant drawback of the case study method is its susceptibility to researcher bias during interpretation. Because the researcher is deeply involved in collecting and analyzing the data, their personal expectations or theoretical perspectives can unintentionally influence the conclusions drawn from the study.

Disadvantage of Case Studies: Researcher Bias

A researcher spends three years living with and documenting the life of a single, isolated individual who has had no contact with modern technology. The researcher's goal is to draw broad conclusions about the fundamental nature of human cognition without technological influence. What is the most significant scientific limitation of using this single-person investigation to achieve this specific goal?

Case studies offer a level of detailed analysis that is difficult to achieve with other research methods, providing deep insights that can guide future controlled research. They are frequently the only viable method for studying rare conditions, as obtaining a large enough sample for quantitative studies is often impossible. Furthermore, while they typically focus on atypical cases, the in-depth examinations provided by case studies can yield profound insights into normal psychological functioning and inspire the formulation of new theories and hypotheses.

Benefits of Case Studies

While case studies are useful for generating hypotheses, they have significant methodological limitations and should never be used as empirical evidence to support theories. They lack the strict experimental controls necessary for internal validity, making it impossible to determine causation or rule out alternative explanations. Additionally, because they typically focus on a single, often atypical individual, case studies suffer from poor external validity, meaning their findings cannot be generalized to the broader population. Finally, case studies are particularly susceptible to researcher bias, as the subjective nature of the analysis provides ample opportunity for the researcher's theoretical views to influence the case description.

Limitations of Case Studies

Henry Molaison (H.M.) is one of psychology's most famous case studies. In 1953, surgeons removed large sections of his hippocampus to treat severe epilepsy. While the surgery successfully stopped his seizures without affecting his IQ or personality, it left him with anterograde amnesia. His short-term memory remained intact, but he permanently lost the ability to transfer new information into long-term memory—a process known as consolidation. This case was crucial for memory research because it demonstrated a clear dissociation between short-term and long-term memory and highlighted the temporal lobes' essential role in memory consolidation.

Case of Henry Molaison (H.M.)

The case of Anna O. is an influential case study used by Sigmund Freud to illustrate the principles of psychoanalysis. Anna experienced severe physical and psychological symptoms, such as an inability to drink, which Freud attributed to repressed emotions from a traumatic incident. When she recalled the memory under hypnosis, her symptoms vanished. While this case effectively illustrates psychoanalytic theory, it is considered worthless as empirical evidence because its observational nature cannot rule out alternative explanations, prove causation, or determine if her experience was typical.

Case of Anna O.

The Little Albert experiment, conducted by John Watson and Rosalie Rayner in 1920, is an influential case study in the history of psychology. The researchers repeatedly paired a loud noise with the approach of a white rat, which taught the young child to fear the rat along with other furry objects. This detailed observation of a single individual demonstrated how emotional responses could be conditioned.

The Little Albert Experiment

Although both single-subject research and case studies focus in detail on a small number of participants, they differ fundamentally in methodology and data analysis. Case studies represent a qualitative approach focused on understanding people's subjective experience through observation, resulting in relatively unstructured data (such as detailed interviews) that is analyzed using narrative techniques. Conversely, single-subject research is a quantitative approach that seeks to understand objective behavior through strict experimental manipulation and control, yielding highly structured data that is analyzed quantitatively.

Comparison of Single-Subject Research and Case Studies

Sigmund Freud used the case study of 'Anna O.' (Bertha Pappenheim) to illustrate the principles of his psychoanalytic theory. She presented with odd physical and psychological symptoms, such as an inability to drink fluids, which Freud attributed to a repressed memory of a dog drinking from a glass. He claimed that recalling this event and expressing the repressed emotion under hypnosis cured her symptom. While the case effectively illustrates psychoanalytic concepts, it lacks evidentiary value for the theory because it is impossible to verify if the repression caused the symptom or if recalling the trauma led to the cure.

Case Study of Anna O.

Which statement accurately describes the type of data collected in a psychological case study?

A researcher conducts an in-depth, year-long investigation of a single patient with a rare memory disorder. The researcher collects detailed interview transcripts, behavioral observations, and also administers standardized neuropsychological tests that yield numerical scores. Because the study includes these numerical test scores, it no longer qualifies as a case study.

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