Idiographic and nomothetic approaches to psychological investigation.

The idea

An idiographic approach studies the individual in depth and treats subjective experience as the data. Freud built much of psychosexual theory on one boy, Little Hans, and the memory models rest on case studies of single brain-damaged patients; the methods are case studies, unstructured interviews and thematic analysis. A nomothetic approach studies many people to produce general laws, norms and predictions using standardised measures and statistical testing. Radford and Kirby split those laws into three: classifying people into groups, as diagnostic manuals do; stating principles of behaviour, as conditioning does; and placing people on dimensions, as Eysenck did by factor-analysing questionnaires from hundreds of servicemen. The real distinction is about generalisation, not about numbers.

What earns the marks

• Idiographic: the individual is studied as unique, with no attempt to measure them against a general standard.
• Idiographic methods: case study, unstructured interview and qualitative or thematic analysis, producing rich subjective data.
• Idiographic examples: Freud's Little Hans, single-patient studies of amnesia, and the humanistic focus on personal experience.
• Nomothetic: large samples are studied to establish general laws, norms and predictions through standardised quantitative measurement.
• Radford and Kirby's three kinds of law: classifying people into groups, establishing principles of behaviour, and placing people on dimensions.
• Nomothetic examples: diagnostic classification, the laws of conditioning, and Eysenck's personality dimensions derived by factor analysis.
• AO3: a single case can generate hypotheses and can falsify a general law outright, which is why the idiographic approach is not unscientific.
• AO3: it also rests on subjective interpretation and tiny samples, with no comparison baseline, so findings cannot be generalised.
• AO3: the nomothetic approach is replicable and predictive but loses the person, since a group probability describes nobody in particular; most approaches use both, so the dichotomy may be false.

Common mistakes and how to put them right

• Treating idiographic as a synonym for qualitative and nomothetic for quantitative.

  Put it right: The method usually follows, but the distinction is about whether a general law is the goal.

• Asserting that case studies cannot be scientific.

  Put it right: One contrary case can refute a general law, which is about as scientific as evidence gets.

• Assigning a whole approach to one side.

  Put it right: The biological approach uses idiographic case studies of patients alongside nomothetic averages.

• Describing the approaches without naming a single method, so 'studies individuals' sits there with no case study or interview attached.

Exam tips

• Classification questions are common: check the sample size and whether the aim was a general law before you commit to an answer.
• A comparison scores best when each paragraph holds both approaches against one criterion, rather than dealing with them one after the other.
• Close on the complementary-not-competing line, backed by a named approach that demonstrably uses both.