Nomothetic Idiographic Debate in Psychology

The Nomothetic Approach

The term “nomothetic” comes from the Greek word “nomos,” meaning “law.”

Psychologists who adopt this approach are mainly concerned with studying what we share with others (i.e., similarities between people).

Therefore, the nomothetic approach involves establishing laws or generalizations that apply to all people.

Laws can be categorized into three kinds:

(1) Classifying people into groups (such as the DSMIV for classifying people with mood disorders );

(2) Establishing principles (Such as the behaviorist laws of learning ), and

(3) Establishing dimensions (such as Eysenck’s personality inventory which allows for comparisons between people).

This approach typically uses scientific methods such as experiments and observations to obtain quantitative data. Group averages are statistically analyzed to create predictions about people in general.

Personality: – A Nomothetic Approach

The psychometric approach to the study of personality compares individuals in terms of traits or dimensions common to everyone. This is a nomothetic approach, and two examples are Hans Eysenck’s type and Raymond Cattell’s 16PF trait theories.

The details of their work need not concern us here. Suffice it to say they both assume that there are a small number of traits that account for the basic structure of all personalities and that individual differences can be measured along these dimensions.

In the past 20 years, a growing consensus has begun to emerge about what those traits are.  The “big 5” are considered to be extroversion, agreeableness, conscientiousness, emotional stability, and openness to experience.

From a nomothetic point of view, these are considered to describe the psychologically significant aspects of any personality adequately.


Regarded as scientific as it is: precise measurement; prediction and control of behavior; investigations of large groups; objective and controlled methods allowing replication and generalization.

Has helped psychology as a whole become scientific by developing laws and theories which can be empirically tested.


Predictions can be made about groups, but these may not apply to individuals.

The approach has been accused of losing sight of the ‘whole person.’

The Idiographic Approach

The term “idiographic” comes from the Greek word “idios” meaning “own” or “private.” Psychologists interested in this aspect of experience want to discover what makes each of us unique.

No general laws are possible because of chance, free will and the uniqueness of individuals.

The approach tends to include qualitative data, investigating individuals in a personal and detailed way.
Methods of research include case studies, unstructured interviews, self-reports, autobiographies, and personal documents.

Personality: – An Idiographic Approach

At the other extreme, Gordon Allport found over 18,000 separate terms describing personal characteristics.

Whilst some of these are common traits (that could be investigated nomothetically), the majority, in Allport’s view, referred to more or less unique dispositions based on life experiences peculiar to ourselves.

He argues that they cannot be effectively studied using standardized tests. What is needed is a way of investigating them ideographically.

Carl Rogers, a Humanist psychologist, has developed a method of doing this, a procedure called the “Q-sort.” First, the subject is given a large set of cards with a self-evaluative statement written on each one.

For example, “I am friendly” or “I am ambitious,” etc. The subject is then asked to sort the cards into piles. One pile contains statements that are “most like me,” one statement that are “least like me,” and one or more piles for statements that are in-between.

In a Q-sort, the number of cards can be varied, as can the number of piles and the type of question (e.g., How I am now?

How did I use to be? How does my partner see me? How would I like to be?) So there are a potentially infinite number of variations. That, of course, is exactly as it should be for an idiographic psychologist because, in his/her view, there are ultimately as many different personalities as there are people.


A major strength of the idiographic approach is its focus on the individual. Gordon Allport argues that it is only by knowing the person as a person that we can predict what the person will do in any given situation.

Findings can serve as a source of ideas or hypotheses for later study.


The idiographic approach is very time-consuming. It takes a lot of time and money to study individuals in depth. If a researcher uses the nomothetic approach, once a questionnaire, psychometric test, or experiment has been designed, data can be collected relatively quickly.


Idiographic and nomothetic approaches should not be seen as conflicting. It is more helpful to see them as complementary.

The insights from an idiographic approach can shed more light on the general principles developed using the nomothetic approach.

For example, Bowlby’s theory of maternal deprivation suggests that extreme maternal deprivation is irreversible. This theory was developed using a nomothetic approach.

However, the case of Koluchova’s twins demonstrates that in this single, idiographic case, maternal deprivation was overcome. Bowlby’s theory can therefore be challenged.

As always, it is best to take a combined approach. Millon & Davis (1996) suggest research should start with a nomothetic approach, and once general ‘laws’ have been established, research can then move to a more idiographic approach. Thus, getting the best of both worlds!

Olivia Guy-Evans

BSc (Hons), Psychology, MSc, Psychology of Education

Associate Editor for Simply Psychology

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

Saul Mcleod, PhD

Educator, Researcher

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.