This is one of the main philosophical debates in psychology.
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. That is to say in establishing laws or generalizations.
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.
Despite the fact that an important aspect of our uniqueness is our genes (i.e. it comes from biology) the distinction between the nomothetic and the idiographic is often equated with two types of science the natural sciences concerned with discovering laws of nature and the social sciences with individual meanings. We can examine these differences further by seeing how they relate to personality theory.
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 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 adequately describe the psychologically significant aspects of any personality.
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 standardised tests. What is needed is a way of investigating them idiographically.
Two psychologists who have developed methods of doing this are George Kelly with his repertory grid technique and Carl Rogers who has made extensive use of a procedure called the “Q-sort”. What this entails is as follows. 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 to contain statements that are “most like me”, one statements 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 I used to be? How my partner sees me? How I would 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.
From these examples we can see that the difference between a nomothetic and an idiographic approach is not just a question of what the psychologist wants to discover but also of the methods used. Experiments. correlation, psychometric testing and other quantitative methods are favoured from a nomothetic point of view. Case studies, informal interviews, unstructured observation and other qualitative methods are idiographic.
There are also broad differences between theoretical perspectives. Behaviorist, cognitive and biological psychologists tend to focus on discovering laws or establishing generalizations. The humanists are interested in the individual. As in so many other debates psychoanalysis is difficult to pin down. Thus it could be seen as nomothetic if one were to concentrate on Freud’s view of the psychic apparatus common to us all (id, ego, superego). On the other hand each patient represents a new challenge for therapy with a configuration of defense mechanisms that is all their own and an illness that derives from unique childhood experiences.
McLeod, S. A. (2007). Nomothetic Idiographic Debate. Retrieved from www.simplypsychology.org/nomothetic-idiographic.html