Overview – Case studies

A case study is an in-depth, detailed investigation of a single individual, small group, institution, or event. So, rather than scanning large populations for broad trends, case studies focus on a single subject to gain a rich and detailed understanding of complex behaviours, experiences, and psychological processes.

Case studies often draw on other research methods discussed elsewhere such as observations, interviews, diaries, and psychometric tests to build a comprehensive picture of the subject.

Features of a case study

A case study looks at a single individual, small group, or event in great depth. Unlike experiments or correlations, researchers aren’t trying to manipulate variables or collect data from large samples. Instead, the aim is to build a detailed picture of one unique case by combining evidence from multiple sources.

Common features of case studies include:

  • Focus on a single case: The research centres on one individual, small group, institution, or event.
  • Unique or unusual cases: Case studies often investigate unusual individuals, groups, or events rather than typical ones. This is because unique cases are difficult to study using other research methods.
  • Qualitative data: As most case studies focus on a single subject, the data tends to be qualitative rather than quantitative. However, quantitative data (e.g. test scores or brain scans) may also be included.
  • Multiple sources of evidence: Researchers often combine observations, interviews, questionnaires, psychometric tests, medical records, diaries, or official documents. This ‘methodological triangulation’ enables researchers to compare evidence from one method with evidence from another.
  • Real-life context: Behaviour is studied within its natural setting rather than under artificial laboratory conditions.
  • Longitudinal approach: Many case studies collect data over weeks, months, or even years to examine how behaviour changes over time.

Examples of case studies

  • Freud (1909): An in-depth investigation of a young boy called Hans. It combined interviews, letters from Hans’ father, and qualitative observations to understand the development of his horse phobia.
  • Sperry (1968): A detailed investigation of a small group of individual split-brain patients. Although the research was primarily a quasi-experiment, Sperry also carried out extensive individualised testing of each patient.

Evaluation: Case studies

Strengths of case studies:

  • Rich qualitative data: Case studies provide detailed information about behaviour, experiences, and psychological processes that would be missed by large-scale studies. For example, researchers can explore how a patient copes with a brain injury by combining interviews, observations, and medical records over several years. This gives insight into how the subject thinks and feels – not simply what they do.
  • Enables study of unique phenomena: Allows psychologists to investigate rare conditions or unusual individuals (e.g. Little Hans’ phobia or split-brain patients) that could not be created experimentally.
  • Generates hypotheses for future research: Findings can inspire new theories and experiments that can later be tested using larger samples.

Weaknesses of case studies:

  • Low generalisability/low population validity: Findings from one person or small group may not apply to the wider population. For example, Freud’s conclusions about Little Hans’ phobia were based on a single five-year-old boy, so they can’t be assumed to explain how phobias develop in all children.
  • Subjectivity and researcher bias: Researchers may interpret qualitative evidence differently or become too personally involved, reducing objectivity. For example, Freud (1909) interpreted Little Hans’ fear of horses as evidence to support his theory of the Oedipus complex. However, other psychologists have argued that Little Hans’ phobia could have been explained in other ways – such as the fact that Hans witnessed a horse collapse in the street when he was young.
  • Low replicability: Case studies are often highly unique and depend on specific individuals, contexts, and circumstances, which makes it difficult for other researchers to repeat the exact same investigation. For example, a case study of a rare brain injury can’t easily be replicated if researchers can’t find another person with the same condition.

Obtaining data for case studies

To conduct a case study, researchers gather detailed information about a single individual, small group, institution, or event. Rather than relying on one research method, psychologists usually combine several sources of data to build a comprehensive understanding of the case.

Examples of data used in case studies includes:

  • Observations: Recording behaviour as it naturally occurs or within controlled settings.
  • Interviews: Conducting structured, semi-structured, or unstructured interviews to explore participants’ thoughts, feelings, and experiences.
  • Psychometric tests: Using standardised tests to measure traits or abilities (e.g. IQ, memory, personality, or mental health).
  • Official records and documents: E.g. school reports, medical records, hospital notes, legal documents,historical archives, etc.
  • Diaries and personal accounts: Analysing letters, journals, or diary entries to understand behaviour over time.

Psychologists may then combine data sources like those above and use methodological triangulation. For example, a researcher studying a patient with a brain injury might combine interviews about their experiences, observations of their behaviour, results from psychometric tests, and medical records. Using several sources of evidence like this enables researchers to compare findings across different methods. This makes it more likely that the conclusions are valid and mitigates the limitations of relying on a single source of data.

When conducting a case study, researchers must carefully consider how evidence is collected, organised, and interpreted to ensure the conclusions are as valid and reliable as possible:

  • Multiple sources of evidence: Using several methods allows researchers to compare findings across different sources, improving confidence in their conclusions (triangulation).
  • Longitudinal data: Many case studies collect information over extended periods to examine changes in behaviour or development.
  • Ethical considerations: Because case studies often involve sensitive personal information or vulnerable individuals, maintaining confidentiality, informed consent, and privacy is particularly important.

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