Idiographic and nomothetic approaches | AQA A-Level Psychology Revision
- Revision Notes
- Aug 5
- 24 min read
Updated: 5 days ago
For 7182 specification, first teach in September 2025
AQA A-Level Psychology | Free Revision Notes
Estimated study time: 50 minutes
Idiographic and nomothetic approaches differ in what psychologists aim to discover about behaviour. This Idiographic and nomothetic approaches A-Level Psychology revision page examines intensive investigation of unique individuals and the search for general laws that apply across populations. You will compare the methods, evidence and conclusions associated with each approach. The debate follows naturally from questions about the level at which behaviour should be investigated and is especially important when evaluating generalisation, scientific methods and individual experience.
Learning Objectives 🎯
By the end of this revision page, you should be able to:
Define idiographic and nomothetic investigation.
Explain the aims and methods associated with each approach.
Distinguish an approach to investigation from a particular research method.
Apply both approaches to unfamiliar research scenarios.
Compare the strengths and limitations of idiographic and nomothetic research.
Explain how the two approaches may complement one another.
Revision Notes 📚
Idiographic and nomothetic approaches A-Level Psychology revision: the central debate
The idiographic-nomothetic debate concerns the aim of psychological investigation.
Psychologists may aim to:
understand the unique experiences of a particular individual
identify broad patterns and construct general laws of behaviour
The idiographic approach focuses on uniqueness and detailed investigation of individuals.
The nomothetic approach focuses on similarities between people and the development of general principles that can be applied to a wider population.
The AQA specification identifies idiographic and nomothetic approaches to psychological investigation as part of Issues and Debates in Psychology. Students may be expected to illustrate this debate using topics studied elsewhere in the course.
The idiographic approach
The idiographic approach investigates the behaviour and experiences of a particular individual, or a very small number of individuals, in considerable depth.
Its main purpose is to understand:
what makes the person unique
how the person experiences their situation
the meaning the person gives to events
how different aspects of the person’s life connect
why the individual behaves as they do
The individual is not treated simply as one data point within a larger group.
An idiographic researcher is interested in a detailed account of the person rather than comparing them with an average participant.
The idiographic focus on uniqueness
The idiographic approach assumes that important information may be lost when a person’s behaviour is reduced to a group score.
For example, two people may receive the same score on a questionnaire but have:
different reasons for their answers
different personal histories
different emotional experiences
different ways of understanding the situation
different combinations of influences on their behaviour
An idiographic investigation aims to explore these differences.
The approach is therefore particularly valuable when the researcher wants to understand a person’s subjective experience rather than establish how common that experience is.
Subjective experience
Subjective experience is the person’s individual perception and interpretation of events.
It includes:
thoughts
feelings
beliefs
personal meanings
memories
interpretations of relationships and situations
Two people may experience the same event differently because they understand and interpret it in different ways.
An idiographic researcher may therefore ask:
How did the person experience the event?
What meaning did it have for them?
How did it affect their thoughts and feelings?
How does it connect with their previous experiences?
How does the person explain their own behaviour?
Methods associated with idiographic investigation
Idiographic research commonly involves methods capable of producing detailed information.
These may include:
case studies
unstructured interviews
detailed observations
personal accounts
diaries or journals
single-case experiments
The 2025 mark scheme described idiographic research as focusing on individual behaviour and experience, often through case studies, single-case interviews, experiments or observations.
You can review the strengths and limitations of intensive individual research through detailed investigation of a person or small group.
The case study method
A case study is an in-depth investigation of an individual, group, institution or unusual event.
A case study may draw on several sources of information, such as:
interviews
observations
psychological tests
personal records
reports from relatives
historical information
Using several sources may create a detailed picture of the case.
Case studies often support idiographic aims because the researcher examines the participant’s unique characteristics and circumstances.
However, a case study is a method, while idiographic investigation is an approach or aim. The terms should not be treated as exact synonyms.
Unstructured interviews
An unstructured interview allows the interviewer to explore the participant’s answers in depth.
The interviewer can:
ask follow-up questions
request clarification
explore unexpected responses
allow the participant to describe experiences in their own words
adapt the conversation to the individual
This makes unstructured interviewing suitable for investigating subjective experience.
You can compare this with more standardised approaches through structured and unstructured self-report investigation.
Detailed observations
A researcher may observe one person repeatedly across situations or over time.
This could help the researcher understand:
how behaviour changes with context
what events precede particular responses
how the individual interacts with others
whether behaviour follows a unique pattern
The purpose is to build a detailed account of that person rather than estimate the frequency of behaviour across a population.
Single-case experiments
Idiographic investigation does not have to rely entirely on interviews or qualitative descriptions.
A single-case experiment may involve:
measuring one person’s behaviour
introducing or changing a condition
measuring the same person again
examining changes within that individual
The data may be numerical, but the investigation remains idiographic if its central aim is to understand that particular case rather than formulate a general law.
Qualitative data and idiographic research
Idiographic investigations often collect qualitative data.
Qualitative data are non-numerical and usually expressed in words. They may provide information about:
personal experiences
explanations
attitudes
emotions
individual meanings
This kind of data can be rich and detailed.
However, idiographic and qualitative are not identical terms.
Idiographic describes the aim of understanding the individual.
Qualitative describes the form of the data.
An idiographic study may collect numerical information, while qualitative data may be gathered from a larger sample.
Understanding this distinction is important when revising different forms of psychological data.
Idiographic research and general laws
The idiographic approach does not primarily aim to produce universal laws of behaviour.
A researcher may avoid claiming:
that every person will behave in the same way
that one individual represents a whole population
that the findings can be automatically generalised
that the same explanation applies to every case
The value of the investigation lies in understanding the case itself.
This does not mean that idiographic findings can never contribute to wider psychological knowledge. A detailed case may:
suggest a new hypothesis
identify a process that had previously been overlooked
reveal an exception to an accepted explanation
challenge the claim that a theory applies universally
provide a starting point for larger investigations
An idiographic investigation of attachment
Imagine that a psychologist wants to investigate attachment behaviour idiographically.
The psychologist might:
select one child and caregiver
observe them repeatedly in different situations
interview the caregiver about their experiences
examine changes in the relationship over time
produce a detailed account of this particular attachment relationship
The researcher would not use this single case to claim that all children behave in the same way.
This can be contrasted with the standardised investigation of attachment patterns, where observations from a sample were used to identify attachment types.
An idiographic investigation of obedience
A psychologist investigating obedience idiographically might conduct an in-depth interview with one person who had faced pressure from an authority figure.
The researcher could explore:
what the person thought during the situation
why they obeyed or resisted
how they understood the authority figure
which previous experiences influenced their response
how they felt afterwards
The aim would be to understand the person’s unique experience rather than estimate the percentage of people who would obey.
The humanistic approach and idiographic investigation
Humanistic Psychology is closely associated with idiographic investigation.
Humanistic psychologists emphasise:
subjective experience
personal meaning
free will
individual growth
the uniqueness of the person
They are less concerned with reducing behaviour to general laws that apply identically to everyone.
The idiographic emphasis on the individual therefore fits closely with the whole person, personal meaning and self-development.
This does not mean that every investigation inspired by humanistic ideas must use the same method. The connection concerns the shared emphasis on individual experience.
Strengths of the idiographic approach
Rich and detailed information
Idiographic research can produce an extensive account of behaviour.
Instead of reducing a participant to a score, the researcher may examine:
the person’s background
the sequence of events
their thoughts and feelings
the meaning of their behaviour
changes over time
the interaction of several influences
This provides depth that may not be available from standardised group research.
Meaningful understanding
A behaviour may only be fully understood when its meaning to the individual is considered.
For example, two people may avoid the same situation for very different reasons. A group measure might record identical avoidance, while an idiographic investigation could reveal the different explanations.
The findings may therefore have greater personal and contextual meaning.
Usefulness in clinical contexts
Idiographic investigation can be useful when psychologists work with individual clients.
A psychologist may need to understand:
the person’s particular symptoms
their history
the situations that trigger difficulties
how they interpret events
their response to treatment
A general law may provide a useful starting point, but support must often be adapted to the individual.
The 2025 mark scheme identified clinical contexts as an area in which understanding subjective individual experience may be particularly useful.
Investigation of unusual cases
Some psychological phenomena are rare. It may be impossible to recruit a large sample of people with the same characteristics.
An intensive investigation can still provide valuable evidence about:
unusual behaviour
rare experiences
exceptional development
the consequences of a particular event
Without idiographic research, these cases might not be investigated at all.
Challenging established theories
One carefully investigated case can expose a limitation in a theory.
If a theory claims that everyone must behave in a particular way, one clear exception may show that the claim is too broad.
The case does not necessarily disprove every part of the theory, but it may lead psychologists to:
revise the explanation
limit its conclusions
investigate additional variables
reconsider a claim of universality
Generating hypotheses
Idiographic research may identify patterns or explanations that can later be tested nomothetically.
A detailed interview, observation or case study may suggest:
a possible relationship between variables
a new explanation
an overlooked influence
a prediction for future research
The idiographic investigation can therefore be the first stage in a wider research programme.
Limitations of the idiographic approach
Limited generalisability
Findings from one person cannot automatically be applied to everyone else.
The participant may be unusual because of their:
background
personal history
characteristics
social situation
particular combination of experiences
The findings may accurately describe the individual while having limited relevance to the wider population.
Subjective interpretation
Detailed qualitative information often requires the researcher to interpret what the participant says or does.
Different researchers may:
focus on different details
assign different meanings to the same response
reach different conclusions
be influenced by their own expectations
This may reduce objectivity.
Difficulty with replication
An individual’s life and circumstances cannot always be recreated.
The procedure may also change as the researcher follows unexpected information or adapts questions to the participant.
This can make exact replication difficult.
Less scientific appearance
Idiographic methods are sometimes criticised for being less scientific because they may involve:
subjective interpretation
small samples
procedures that are not fully standardised
limited hypothesis testing
findings that cannot be generalised
However, this criticism should be applied carefully. A single-case experiment can still use systematic measurement, operationalised variables and controlled procedures.
Time and resources
Investigating one individual in depth may require:
repeated contact
lengthy interviews
detailed transcription
analysis of large amounts of information
examination of several data sources
This can be time-consuming, particularly when the findings apply primarily to one case.
The nomothetic approach
The nomothetic approach investigates groups of people to identify broad patterns, establish general laws and make predictions about behaviour.
Its main purpose is to discover:
what people have in common
which variables are related
how behaviour can be classified
whether a general explanation is supported
whether findings can be applied to a wider population
Rather than concentrating on one person’s unique experience, nomothetic research compares participants and searches for regularities.
General laws
A general law is a broad principle intended to explain or predict behaviour across many people.
Examples of nomothetic conclusions might take the following forms:
people are more likely to behave in a particular way under specified conditions
a particular factor affects behaviour
individuals can be classified into different types
a psychological process follows a general pattern
one variable is related to another
General laws usually describe probabilities or patterns. They do not necessarily mean that every individual will behave identically.
Large samples
Nomothetic research commonly investigates a larger sample than idiographic research.
A larger sample allows the researcher to:
compare participants
calculate group patterns
identify similarities and differences
use statistical analysis
draw cautious conclusions about a wider population
The sample should represent the population to which the researcher intends to generalise.
This creates an important link with the relationship between a sample and its target
Methods associated with nomothetic investigation
Nomothetic researchers may use:
controlled experiments
questionnaires
structured interviews
standardised observations
correlations
psychological tests
The particular method can vary. What makes the investigation nomothetic is its aim to identify general patterns and apply conclusions beyond the individuals studied.
Standardisation
A nomothetic investigation often uses a standardised procedure.
This means participants experience:
the same instructions
the same tasks
the same questions
the same timings
the same measurement system
Standardisation makes it easier to compare participants fairly.
It also allows other psychologists to repeat the procedure.
Quantitative data
Nomothetic research often collects quantitative data, which are expressed numerically.
Examples include:
test scores
frequencies
response times
ratings
percentages
questionnaire totals
Numerical data can be statistically analysed to identify patterns within the sample.
As with idiographic research, this is a common association rather than a complete definition. The nomothetic approach is defined by its search for general laws, not simply by its use of numbers.
Hypothesis testing
A nomothetic investigation may begin with a testable hypothesis.
For example:
Participants exposed to a unanimous majority will show greater conformity than participants exposed to a non-unanimous majority.
Researchers can then:
operationalise the variables
collect data from a sample
compare the conditions
analyse the results
decide whether the evidence supports the hypothesis
draw conclusions about the wider behaviour
This aligns the nomothetic approach with objectivity, empirical investigation and hypothesis testing.
Statistical analysis
Nomothetic researchers may use descriptive and inferential statistics.
Descriptive statistics summarise the sample through:
averages
measures of dispersion
frequencies
percentages
graphs and tables
Inferential tests help researchers decide whether a pattern is statistically significant and whether it may extend beyond the sample.
Statistical significance does not guarantee that findings apply universally. Generalisation also depends on:
the sample
the procedure
the validity of the measures
the population represented
the contexts in which the research was conducted
A nomothetic investigation of obedience
Milgram investigated obedience using a sample of participants exposed to a standardised procedure.
The research contributed to general explanations of how situational factors may influence obedience.
This is nomothetic because the investigation was not limited to understanding one participant’s unique experience. Findings from the sample were used to develop broader explanations and predictions about obedience.
You can connect this debate to research into the effects of proximity and location.
The 2022 mark scheme accepted Milgram’s use of a participant sample to support a theory of situational obedience as an illustration of nomothetic investigation.
A nomothetic investigation of attachment
Ainsworth used the Strange Situation to observe infant-caregiver behaviour using standardised episodes.
Patterns across the sample contributed to the identification of attachment types.
This is nomothetic because:
several infants were investigated
behaviour was measured using common criteria
similarities were identified
general categories were constructed
the categories were intended to apply beyond each individual case
The 2022 mark scheme also accepted Ainsworth’s use of a sample to establish attachment types as a nomothetic example.
Developing an idiographic investigation nomothetically
Suppose a psychologist has interviewed one person in depth and identified a possible connection between social support and resistance to authority.
To develop the research nomothetically, the psychologist could:
recruit a larger and more representative sample
formulate a testable hypothesis
operationalise social support and resistance
use the same procedure with each participant
collect quantitative data
analyse the findings statistically
determine whether the pattern applies across the sample
draw cautious conclusions about the wider population
AQA specimen material emphasised larger samples, representativeness, testable hypotheses, quantitative analysis and general conclusions when developing idiographic research through a nomothetic approach.
Strengths of the nomothetic approach
Development of general laws
Nomothetic research allows psychologists to move beyond individual cases and establish broader explanations.
General laws can help psychologists:
organise findings
explain common behaviour
make predictions
construct models
compare populations
test whether an explanation applies widely
This supports Psychology’s aim of developing a systematic body of knowledge.
Scientific methods
Nomothetic research is often compatible with scientific investigation.
Researchers can use:
testable hypotheses
operationalised variables
standardised procedures
controlled conditions
quantitative measurements
statistical analysis
These features can increase objectivity and replicability.
Prediction
A general law may allow psychologists to predict how people are likely to behave under particular conditions.
A prediction will not necessarily be correct for every person. It may still identify a reliable probability across a population.
Practical applications
General findings can contribute to interventions intended for many people.
For example, nomothetic research may be used to:
develop treatments
identify patterns of risk
design educational strategies
predict responses to social situations
classify behaviour
compare the effectiveness of interventions
Comparison between people and groups
Standardised measurements allow researchers to compare:
individuals
groups
conditions
changes over time
different treatments
Without common measurements, it would be difficult to determine whether a pattern extends beyond one person.
Replicability
A standardised nomothetic procedure can be repeated by other researchers.
Replication helps psychologists decide whether a result is:
reliable
dependent on one sample
found in different settings
consistent over time
Limitations of the nomothetic approach
Loss of individual experience
Group averages may conceal important differences.
Suppose the average score for a group is 20. This does not reveal:
why individuals obtained their scores
whether everyone responded similarly
the meaning of the task to each participant
whether different processes produced the same score
The statistical pattern may accurately describe the group while failing to explain a particular individual.
The average person may not exist
A group mean is a mathematical summary. No individual participant has to match it exactly.
Psychologists should therefore be cautious when applying an average pattern directly to one person.
Limited personal meaning
Standardised questions and response options may prevent participants from fully explaining their experiences.
The resulting data may be easier to compare but less detailed or personally meaningful.
General laws may become overgeneralised
A researcher may claim that findings apply to a population not properly represented by the sample.
A nomothetic study is only generalisable when:
the sample is appropriate
the measures are valid
the relevant groups are represented
the conclusion stays within the evidence
A large sample does not automatically justify a universal conclusion.
Reduction of complex behaviour
Nomothetic researchers may reduce behaviour to measurable variables so that it can be compared statistically.
This can improve scientific control, but it may overlook the whole person and their social context.
The connection between general measurement and simplified explanation links this debate to different levels of psychological explanation.
Classification can obscure variation
Nomothetic research may place people into types or categories.
Categories can be useful, but individuals placed in the same category may still differ in important ways.
A classification should not be treated as a complete description of the person.
Idiographic and nomothetic approaches compared
Feature | Idiographic approach | Nomothetic approach |
Main aim | Understand a unique individual | Establish general laws and patterns |
Focus | Individual experience and uniqueness | Similarities and comparisons between people |
Typical sample | One person or a very small number | A larger sample |
Typical methods | Case studies, unstructured interviews, detailed observations, single-case investigations | Experiments, structured self-reports, standardised observations, tests and correlations |
Typical data | Often qualitative and detailed | Often quantitative and suitable for statistical analysis |
Procedure | May be flexible and adapted to the person | Usually standardised across participants |
Generalisation | Not usually the primary aim | A major aim |
Main strength | Rich, meaningful understanding | Prediction and general laws |
Main limitation | Limited generalisability | Loss of individual meaning |
Scientific status | May be less standardised or objective | Often highly standardised, testable and replicable |
Practical value | Supports individual assessment and understanding | Supports interventions and predictions across populations |
The approaches are not simply methods
One of the most important distinctions is between an approach to investigation and a research method.
Research decision | Idiographic or nomothetic? |
Investigating one person to understand their unique experience | Idiographic aim |
Using one person to test a standardised measurement repeatedly | May still be idiographic if conclusions concern that person |
Interviewing 200 participants and searching for a common pattern | Nomothetic aim |
Collecting qualitative responses from a large sample to construct a general theory | Nomothetic aim |
Conducting a case study and then claiming the result applies to everyone | An unjustified nomothetic conclusion from limited evidence |
A method does not automatically determine the approach.
Qualitative does not always mean idiographic
A researcher could interview 100 participants using open questions and analyse the responses to identify a common pattern.
The data are qualitative, but the investigation may be nomothetic because the aim is to establish a general explanation.
Quantitative does not always mean nomothetic
A researcher could measure one individual’s anxiety score every day during treatment.
The data are quantitative, but the investigation may be idiographic because the aim is to understand change in that person.
Exam focus: Identify the aim and conclusion of the investigation, not just whether the data consist of words or numbers.
Generalisation is not the same as comparison
Nomothetic research normally compares people to identify broad patterns.
Idiographic investigation emphasises the individual rather than comparison.
However, the difference is not simply that one approach compares and the other does not. The more important distinction is what the psychologist intends to achieve:
individual understanding
general explanation
Applying the approaches to the same behaviour
The same behaviour can be studied idiographically or nomothetically.
Research question: Why do children display friendly behaviour?
Idiographic investigation | Nomothetic investigation |
Observe one child repeatedly across several settings | Observe a large sample of children |
Interview the child’s caregivers | Use the same behavioural categories for everyone |
Examine the meaning and context of the child’s behaviour | Compare frequencies across different conditions |
Produce a detailed account of this child | Use statistical analysis to identify a general pattern |
Avoid generalising to all children | Draw cautious conclusions about the target population |
A 2021 mark scheme stated that an idiographic version of a nomothetic observation could involve interviewing, observing or conducting a case study of one child, while avoiding general laws about all children.
Applying the approaches to mental health
Idiographic investigation
A psychologist may study one person’s symptoms, thoughts, history and relationships in depth.
This can help the psychologist understand:
the individual pattern of symptoms
personal triggers
the meaning of the experience
the person’s response to treatment
Nomothetic investigation
A psychologist may investigate a large group using standardised measures.
This can help identify:
common characteristics
average treatment effects
relationships between variables
patterns that predict outcomes
Both forms of evidence may be useful. General research can guide treatment, while individual investigation can help adapt that treatment to the person.
Applying the approaches to memory
Idiographic investigation
A psychologist could investigate one person with a particular pattern of memory functioning.
Detailed testing might reveal:
which aspects of memory are affected
which abilities remain
how memory difficulties affect daily life
whether the pattern challenges an existing model
Nomothetic investigation
A psychologist could test a larger sample using a standardised memory task.
The findings might be used to:
compare memory stores or components
estimate common patterns
test a model
make predictions about performance
This can support evaluation of general models of memory functioning.
Idiographic and nomothetic approaches as complementary
The approaches do not have to be treated as complete opposites.
A useful research sequence may be:
An idiographic investigation identifies a detailed pattern.
The pattern is used to generate a hypothesis.
A nomothetic study tests the hypothesis with a larger sample.
A general explanation is proposed.
Further idiographic cases examine how well the explanation fits individuals.
The explanation is refined where necessary.
Each approach addresses a weakness of the other.
Idiographic investigation supplies depth and meaning.
Nomothetic investigation tests breadth and generalisability.
From idiographic evidence to a nomothetic theory
An individual case may reveal a potentially important psychological process.
The researcher can then test whether it appears in a wider population.
For example:
A detailed case suggests that social support helped one person resist authority.
Researchers formulate a hypothesis about social support and resistance.
A larger sample is investigated under standardised conditions.
The results are statistically analysed.
Psychologists decide whether a broader explanation is supported.
The original case does not establish a general law, but it contributes to the development of one.
From nomothetic laws to individual understanding
A general law can provide a useful framework for understanding a person.
However, the psychologist should still investigate:
whether the general pattern applies to this person
which individual circumstances matter
whether the person is an exception
how the behaviour is personally experienced
Nomothetic evidence should guide rather than replace individual assessment.
Evaluating the idiographic approach
Depth is valuable when experience matters
When behaviour is complex or personally meaningful, detailed individual evidence may provide greater insight than a group average.
This is particularly useful when studying:
unusual cases
individual treatment
subjective experience
behaviour that changes with context
Depth does not guarantee accuracy
A large amount of information can still be interpreted incorrectly.
The researcher may:
select evidence that supports expectations
overlook alternative explanations
influence the participant’s responses
interpret ambiguous material subjectively
The quality of idiographic research depends on careful, systematic investigation.
Limited generalisation is not always a failure
The aim of idiographic research is often to understand one individual.
Criticising every idiographic study because it cannot be generalised may miss its purpose.
The more appropriate question is whether the research provides a valid and detailed account of the case.
Individual evidence can influence general Psychology
Although idiographic research does not usually seek general laws, it may contribute to scientific progress by:
generating hypotheses
revealing exceptions
testing the limits of a theory
identifying new variables
showing that an explanation needs revision
Evaluating the nomothetic approach
General laws support prediction and application
Nomothetic research can identify reliable patterns across people.
This supports practical decisions, but predictions should normally be expressed in terms of likelihood rather than certainty.
A general law may predict what people tend to do without determining what every person must do.
Scientific control may increase reliability
Standardisation and quantitative analysis make procedures easier to replicate.
Other researchers can examine whether the pattern appears:
in another sample
in a different setting
at another time
This strengthens confidence in general conclusions.
General laws can neglect exceptions
A theory may explain the majority while failing to explain particular individuals.
Exceptions are scientifically important because they may reveal:
an additional variable
a boundary condition
an alternative process
a limitation in the theory
Nomothetic researchers should not dismiss unusual cases merely because they do not match the average.
Generalisability depends on the sample
A nomothetic aim does not guarantee nomothetic success.
A study may intend to establish a general law but fail because:
the sample is too restricted
the sampling method creates bias
important groups are missing
the measure lacks validity
the procedure does not represent ordinary behaviour
The breadth of a conclusion must match the breadth of the evidence.
Which approach is more scientific?
The nomothetic approach is often viewed as more scientific because it commonly uses:
testable hypotheses
standardised procedures
quantitative data
statistical analysis
replication
general prediction
Idiographic research may appear less scientific when it relies on flexible procedures and subjective interpretation.
However, the contrast is not absolute.
Single-case experiments can be controlled and systematic.
Nomothetic measures can still lack validity.
Numerical data can be collected unreliably.
Qualitative material can be analysed carefully and transparently.
Scientific quality depends on how well the investigation is designed and conducted, not only on its idiographic or nomothetic aim.
Which approach is more useful?
The answer depends on the research purpose.
Research purpose | More suitable emphasis |
Understanding one person’s unique experience | Idiographic |
Investigating a rare case | Idiographic |
Adapting treatment to an individual | Idiographic |
Testing whether a pattern occurs across a population | Nomothetic |
Constructing a general model | Nomothetic |
Comparing treatment outcomes | Nomothetic |
Generating a new hypothesis | Often idiographic initially |
Testing a hypothesis broadly | Nomothetic |
Applying a general explanation to a particular person | A combination |
Building a comparison
A strong comparison directly links the approaches using a common issue.
Weak comparison
Idiographic research uses case studies. Nomothetic research uses experiments.
This is too simplistic and merely describes possible methods.
Developed comparison
Idiographic research prioritises a detailed understanding of an individual, so its findings may have personal meaning but limited generalisability. In contrast, nomothetic research studies samples to establish general laws, increasing the potential for prediction but risking the loss of individual experience.
The developed version compares:
aims
evidence
strengths
limitations
Planning an extended response
A strong discussion of idiographic investigation could use the following structure:
Define the idiographic approach.
Explain its focus on uniqueness and subjective experience.
Describe suitable methods.
Explain the value of rich, qualitative data.
Evaluate limited generalisation and subjective interpretation.
Compare directly with the nomothetic approach.
Apply the debate to a specified topic.
Explain how the approaches may complement one another.
Reach a balanced conclusion.
For an eight-mark question focused on one approach, keep most of the answer focused on that approach. Comparison is valuable only when it helps evaluate the named approach.
Key Words 🔑
Key word | Student-friendly definition | How it may be used in an exam |
Idiographic approach | An approach that investigates an individual or very small number of people in depth, emphasising uniqueness | Identify a study focused on detailed individual experience |
Nomothetic approach | An approach that studies samples to establish general laws, patterns and predictions | Identify research intended to generalise beyond its participants |
Subjective experience | A person’s individual thoughts, feelings and interpretation of events | Explain why idiographic investigation may produce meaningful understanding |
General law | A broad principle intended to explain or predict behaviour across people | Explain the aim of nomothetic research |
Generalisability | The extent to which findings can be applied beyond the participants studied | Compare a central strength of nomothetic research with a limitation of idiographic research |
Case study | A detailed investigation of an individual, group, institution or event | Suggest a method for idiographic investigation |
Single-case investigation | Research that measures or observes one individual intensively | Explain how idiographic research may collect qualitative or quantitative data |
Qualitative data | Non-numerical information, usually expressed in words | Explain how idiographic research may capture personal meaning |
Quantitative data | Numerical information that can be statistically analysed | Explain how nomothetic researchers may compare participants |
Standardisation | Keeping the procedure consistent across participants | Evaluate the replicability of nomothetic research |
Representativeness | The extent to which a sample reflects its target population | Evaluate whether a general law is justified |
Prediction | Using an explanation to state what is likely to happen | Explain a practical advantage of the nomothetic approach |
Individual differences | Ways in which people differ in behaviour or experience | Explain what may be hidden by group averages |
Replication | Repeating an investigation to check whether similar findings are obtained | Evaluate the scientific value of standardised nomothetic research |
Hints from the Examiner Reports 💡
Examiner hint: Define the idiographic approach through its aim, not only its method. Explain that it involves intensive investigation of individual behaviour or experience and prioritises uniqueness rather than general laws.
Examiner hint: Do not write that all idiographic research is a case study. The approach may involve a single-case interview, observation or experiment.
Examiner hint: The 2025 report noted that successful students recognised the focus on intensive individual study, qualitative information and careful investigation of subjective experience.
Examiner hint: Choose examples that genuinely illustrate the aim of the approach. The 2025 report noted that some students cited a case study used to support a universal claim. A study does not become idiographic merely because it examines one person. You must explain whether its aim is individual understanding or generalisation.
Examiner hint: Compare the approaches directly. In 2025, some students described the nomothetic approach without linking it back to the idiographic approach. Those answers gained less credit than reasoned comparisons.
Examiner hint: Use comparative language such as “whereas”, “in contrast” and “however”. Then compare both approaches on the same issue, such as generalisability, depth, prediction or objectivity.
Examiner hint: When outlining nomothetic investigation, include both the sample and the aim. A full explanation should refer to studying a sample and using the findings to establish general laws, make predictions or draw conclusions about a wider population.
Examiner hint: If a question asks you to use a study, explain how the findings were extended beyond the original participants. Simply naming Milgram or Ainsworth is not enough.
Examiner hint: When adapting a nomothetic study idiographically, keep the behaviour the same. The 2022 assessment required students to propose an individual investigation of the same behaviour used in their nomothetic example.
Examiner hint: Avoid confusing idiographic-nomothetic with holism-reductionism. Idiographic-nomothetic concerns the aim of investigation, while holism-reductionism concerns the level of explanation.
Examiner hint: Develop evaluation rather than listing labels. Instead of writing “idiographic research is detailed”, explain how detailed personal accounts may reveal meanings and processes hidden by group averages.
Examiner hint: There are no calculations specific to this lesson. Marks will come from precise definitions, appropriate research proposals and direct comparison.
Common Mistakes ⚠️
Mistake: Defining idiographic research as any study using one participant
Why this is incorrect:
The number of participants alone does not determine the approach. A researcher could study one person while attempting to support a general claim.
How to improve:
Identify whether the investigation aims to understand that individual’s unique experience.
Mistake: Defining nomothetic research as any experiment
Why this is incorrect:
An experiment is a method. Nomothetic investigation is defined by its aim to establish general laws or patterns.
How to improve:
Refer to the sample, comparison, generalisation and prediction.
Mistake: Treating idiographic and qualitative as synonyms
Why this is incorrect:
Idiographic describes the research aim, while qualitative describes the type of data.
How to improve:
Remember that a single-case experiment can collect numerical data.
Mistake: Treating nomothetic and quantitative as synonyms
Why this is incorrect:
Quantitative describes numerical data. A nomothetic researcher could analyse qualitative responses from a large sample to identify a general pattern.
How to improve:
Focus on whether the researcher intends to formulate a broader explanation.
Mistake: Saying that idiographic research produces no useful wider knowledge
Why this is incorrect:
A detailed case can generate hypotheses, identify new variables or challenge an established theory.
How to improve:
Distinguish direct generalisation from contribution to wider theory development.
Mistake: Assuming that a large sample guarantees generalisability
Why this is incorrect:
The sample may still be biased or unrepresentative.
How to improve:
Consider sampling method, population, validity and cultural representation.
Mistake: Criticising an idiographic study only because it cannot be generalised
Why this is incorrect:
Generalisation may not be the aim of the research.
How to improve:
Assess whether the study provides a valid and meaningful understanding of the individual.
Mistake: Assuming all idiographic research is unscientific
Why this is incorrect:
Single-case investigations may use controlled procedures, objective measurement and repeated testing.
How to improve:
Evaluate the actual method and evidence rather than relying on a blanket judgement.
Mistake: Assuming nomothetic research explains every individual
Why this is incorrect:
General laws describe broad patterns and probabilities. Individuals may differ from the average.
How to improve:
Explain that prediction at population level does not guarantee accuracy for every person.
Mistake: Describing both approaches without comparing them
Why this is incorrect:
A comparison question requires direct links between the approaches.
How to improve:
Compare both on a shared issue, such as depth, generalisation, objectivity or practical usefulness.
Mistake: Confusing the debate with holism and reductionism
Why this is incorrect:
Idiographic-nomothetic concerns individual understanding versus general laws. Holism-reductionism concerns whole-person versus component-level explanations.
How to improve:
Identify the exact question being asked before selecting evaluation points.
Mistake: Name-dropping an example
Why this is incorrect:
Writing “Milgram is nomothetic” does not explain why.
How to improve:
State that a sample completed a standardised procedure and the findings were used to produce broader explanations and predictions about obedience.
Exam-Style Questions ✍️
Which one of the following best describes the nomothetic approach?
A. Investigating the unique experience of one personB. Establishing general laws from patterns found in a sampleC. Explaining behaviour at a biological levelD. Studying behaviour without collecting empirical evidence
[1 mark]
Define the idiographic approach to psychological investigation.
[2 marks]
Explain one difference between idiographic and nomothetic investigation.
[3 marks]
A psychologist conducts lengthy, unstructured interviews with one person who experiences panic attacks. The psychologist explores the person’s childhood, relationships, thoughts, emotions and the personal meaning of each panic episode.
Explain why this investigation is idiographic.[4 marks]
A researcher wants to investigate whether social support affects resistance to authority. The researcher recruits 120 participants, uses the same procedure with everyone and compares resistance scores in two conditions.
Explain two features of the investigation that make it nomothetic.[4 marks]
A psychologist has conducted an in-depth case study of one child’s friendly behaviour at school.
Explain how the psychologist could develop the investigation using a nomothetic approach.[6 marks]
Two research teams investigate responses to separation.
Research team | Proposed investigation |
Team A | Repeated observations and interviews involving one child and caregiver over six months |
Team B | A standardised observation completed by 100 child-caregiver pairs, with behaviour classified using the same categories |
Compare the aims and likely findings of the two investigations.[6 marks]
A researcher collects numerical anxiety scores from one participant every day before and during therapy.
Explain why the use of quantitative data does not necessarily make this a nomothetic investigation.[3 marks]
Discuss the idiographic approach to psychological investigation.
[8 marks]
A psychologist argues:
“Psychology needs large samples, standardised procedures and statistical analysis so that it can develop reliable general laws.”
Another psychologist responds:
“Group averages cannot explain the meaning of behaviour to a particular person. Psychology must investigate individual experience in depth.”
Discuss idiographic and nomothetic approaches to psychological investigation. Refer to the psychologists’ statements in your answer.[16 marks]
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