Draft Exam Answer: With reference to trait theory, discuss the differences between the idiographic and nomothetic approach to personality.

With reference to trait theory, discuss the differences between the idiographic and nomothetic approach to personality.

According to trait theorists, personality is simply made up of a collection of traits. The study and measure of the traits an individual possesses allows the formation of ideas and understanding about the type of personality they may have. An understanding of personality allows the prediction of behaviour. There are two different types of trait theory, the idiographic approach and the nomothetic approach. The idiographic approach assumes that each individual possesses traits unique to them, whereas the nomothetic approach assumes all individuals posses the same traits but to varying degrees. The differences between these two approaches will be considered in this essay.

Allport (1960) was one of the founding figures of the study of personality in psychology, emphasising the uniqueness of the individual. Allport found 4500 distinct personality traits which he argued, that whilst some were common traits, the majority referred to more or less unique dispositions.  He organised these into three levels of traits; cardinal traits, central traits and secondary traits. Cardinal traits are the traits that dominate personality and drive individuals acting as a motivating factor, for example competitiveness. Central traits are the traits that best describe an individual and have less impact than cardinal traits; these may be things such as neatness, creativity and persistence. Finally, secondary traits are specific attitudes and habits such as music preference, food choices and clothing style. Allport argues that these cannot be effectively measured or studied using standardised tests and that a more idiographic approach is needed to understand personality fully.

Kelly’s (1955) Repertory Grid is one technique used for identifying the ways that a person construes their experience. It provides information unique to the individual from which inferences about their personality can be made.  Similarly, Rogers (1951) person-centred approach to studying personality is another qualitative method of studying an individual. He developed a method called the Q-sort, similar to Kelly’s (1955) famous repertory grid in which there are an infinite number of variations of answers an individual can give as responses. Other qualitative methods of studying personality are the analysis of case studies, as well as clinical interview techniques, all of which regard the person as unique. This approach has been criticised for being too subjective, and it is argued that a more objective method of inquiry was needed to draw conclusions about personality as a whole.

The nomothetic approach assumes that all individuals possess the same traits but to varying degrees, therefore traits should be regarded as quantifiable variables that can be measured on a scale. It is argued that traits have a number of characteristics; they are seen as stable over time, consistent across the population, for example all individuals have the capacity to be “generous” but to varying degrees, and they are seen as continuous dimensions like height, weight and IQ for example. The study of traits highlights consistent differences among people in their responses to the same stimulus; therefore it is argued that traits can be used to make more generalised predictions about behaviour which can be applied to whole populations. Traits are normally distributed with very few having a strong or weak rating and the majority falling in the middle therefore having a moderate rating. Assumptions can be made about personality and its influence on behaviour by examination of the correlations that occur between the different traits. Factor analysis is used when examination of more than two traits is required. Factor analysis allows researchers to find clusters of correlated traits which they argue form personality factors (Cattell 1905-1998, Eysneck, 1951, Costa & McCrae, 1992). There is much debate about which traits should form personality factors however and how many there should be.

Cattell (ND) took the work of Allport (1960) and reduced the traits down to a more manageable number ending up with his 16 second-order personality factors (16PF). These were organised into two different types of traits, surface traits, made up of traits that exist in many individuals and situations, and source traits which he defined as the underlying traits responsible for the observed variance in the surface traits. Therefore source traits are manifestations of surface traits. Cattell suggested the whole personality could be measured using these 16 personality factors. Cattell’s approach is criticised for being too broad and for failing to acknowledge the subjectivity of measuring personality. It is argued that a personality theory needs to account for both individual differences and varying levels of interpersonal functioning.

Eysneck (1951) attempted to compromise between the work of Allport and Cattell, using factor analysis to develop 3 supertraits, extraversion, neuroticism and psychoticism. These three supertraits which made up the three personality factors in his 3-factor personality model comprise of narrower traits which form these supertraits and can be used to examine the relationship between traits allowing inferences about personality to be made. Eysneck (1951) posits that traits exits in the form of a hierarchy with habits influencing narrower traits which in turn influence the supertraits forming the personality. He suggests that personality can only be influenced by changing traits that exist at the bottom of the hierarchy. Eysneck’s (1951) 3-factor model therefore takes into account environmental factors which Allport’s 16PF failed to do. Eysneck’s 3-factor model was also deeply grounded in biological theory, linking each of his personality factors to different brain mechanisms. For example, he found that levels of extraversion could be explained by different levels of cortical activity and that introverts had higher levels of cortical activity therefore needing to seek less stimulation than extraverts. Neuroticism was also found to be linked to activity in the limbic system, the brain region responsible for emotion processing while psychoticism was found to be linked to differential amounts of testosterone, a hormone that promotes more aggressive and less empathic behaviour.

In conclusion, while the differences between the idiographic and nomothetic approaches can be seen to be the differences in terms of what they are trying to discover; with the idiographic attempting to determine reasons behind personality and behaviour unique to the individual, it can be seen that one of the major differences between the approaches is in the type of experimental method used as well as differences in theoretical perspectives. The idiographic approach favours the humanistic viewpoint, adopting the view that all individuals should be seen as unique, favouring qualitative methods of inquiry such as techniques like Kelly’s (1951) repertory grid, clinical interviews, unstructured observations, and analysis of case studies. The nomothetic approach favours the viewpoint of the behaviourist, cognitive and biological psychologist, preferring quantitative research methods such as experiments, correlations and psychometric testing. The debate therefore leads us to one of methodology; qualitative vs. quantitative, in the subject of personality measurement each of the methods have its advantages and disadvantages. Qualitative methods acknowledge the individual differences between people and their behaviour, consistent similarities between individuals allow for a more in depth theoretical account of personality to be made. Qualitative methods however are able to look at similarities between large cohorts and make generalised assumptions about personality as a whole, this approach does however get criticised for being too objective and the most common measurement of personality today is the “big five” personality scale which is often criticised for being too objective