Psychologists seek to explain and formulate why people behave differently in everyday common situations and to define individual differences in terms of the knowledge gained and it structure. Personality can be defined as an individual’s characteristic qualities of thought, emotion and behaviour when interacting with their social environment. Traits are ‘relatively enduring ways in which an individual differs from another’ (Butt 2012, p. 46). Eysenck’s trait theory has it origins in the psychometric tradition of measurement; while Kelly’s personal construct theory adopts a phenomenological approach. The aims and methods of both theories will be critically compared and contrasted outlining their theoretical perspectives and the knowledge that each produce. By focusing on individual differences their different methodological approaches will be assessed in terms of their objective and subjective roles, highlighting that each have influential findings but don’t completely give a complete account of all personality phenomena. (Butt, 2012)
Eysenck’s (1953) Trait theory adopts a nomothetic approach that classifies personality dimensions to measure and describe the individual differences of personality. It’s based on the assumption that individuals can be characterised by certain personal attributes or traits that in turn influence behaviour. Descriptions of traits have their foundation in everyday language used to describe human behaviour; trait theory draws on the histrionic usage of traits in vocabulary such as ancient Greek typology. This usage is used to support evidence of, ‘constitutional and biological factors that are indicated through personality traits’ (Butt, 2004). Eysenck used factor analysis to establish cluster traits using questionnaires (Eysenck’s Personality Inventory) proposing that two high order factors could account for the clustering profile obtained, extraversion vs introversion and neuroticism vs stability, he later added and third psychoticism vs superego.
Each factor has second order traits established from ‘factor analytic studies’ (Butt, 2012, p.50) to describe more fully individual characteristics or tendencies. Eysenck believed biology could explain the individual differences of personality, that causal factors at a neurological level in the cortical and autonomic arousal systems influence an individual’s temperament and behaviour. ‘The purpose of personality theory is not to capture the idiosyncratic nature of the individual’ (Butt, 2012, p.47), but used as an indicator of how a person is likely to react in certain situations. Eysenck acknowledges that it’s not only biology that influences behaviour, but our past experiences and learning can also have an influence on current reactions to different stimuli. However trait theorists tend to view personality from a deterministic perspective, as stable and enduring and don’t take into consideration the behavioural and attitude changes that people experience over time (Butt, 2012).
Kelly’s (1955) personal construct theory, which is a form of phenomenology; views personality as idiosyncratic phenomena that can not be measured, as each individual adopts a unique way of making sense of their world. Each person is seen as a composition of personal world views or constructs that are based on unique experiences. Individuals construct others behaviour in terms of their own subjective viewpoint. Kelly proposed we act like scientists, who form theories and assumptions about ourselves, others and the world. By inquiry and testing out the uncertainties of our assumptions we produce further inquiry that is an ongoing lifelong cycle. Based on the cognitive approach, it is these constructs or schemas Kelly theorises that provide the basis of our reactions and behaviour (Butt, 2012).
Both Eysenck and Kelly aimed to produce theories that have a clinical application, Eysenck sought to use his theory for clinical diagnosis in response to discredited psychiatric classifications, while Kelly who practised as a psychotherapist sought to facilitate therapeutic change through learning and self awareness. Eysenck viewed ‘classification as a fundamental part of scientific study’ (Eysenck and Rachman, cited in Butt, 2012, p.48), Kelly placed no importance on the psychometric tradition of assessment; the emphasis of his approach is on ‘recognising the value of examining the unique cognitive constructs of an individual’s world view and the self’ (Butt, 2012. p. 47). Kelly’s emphasis was on self-determination and problem solving rather than the diagnostic standardised dimensions used by trait theories.
Where trait theory seeks to discover societal norms and how we all differ in relation to them, personal construct theory places no importance on making individual comparisons through personality dimensions. Butt (2004) states that ‘trait theory does not account for the richness of personality in the way that personal construct theory can’. Trait theory would propose that behaviour is biologically controlled and therefore consistently predictable, which excludes the potential for change, while personal construct theory views constructs as being flexible and fluid and therefore open to change, even through individuals might actively resist the difficulty of change (Butt, 2012).
Mischel (as cited in Butt, 2012) a student of Kelly’s questioned trait theories deterministic view of behaviour consistency, arguing that behaviour was a diverse phenomenon influenced by social stimuli; that people will behave differently according to the situation they find themselves in. Results from Zimbardo’s (1975) prison experiment would suggest that social situations can exert an influencing effect on behaviour. Skinner (1974), (as cited in Butt, 2012) proposed that traits can not explain behaviour; they only provide a description, not an explanation of behaviour that simply identifies regular patterns of behaviour, or a ‘cycle of redescription’ (Butt, 2004. p.3) Mischel also points out that traits are implicit personality theories based on subjective perceptions of the individual being rated, or a perception of others which will reflect biased prejudices of the sociocultural environment. He highlights a study were observers allocated the same traits to both strangers and those they new well, indicating ‘fundamental attribution error’ (Butt, 2004), which suggests that observers attribute over generalised traits that are not valid. This raises the issue of trait objectivity, by highlighting the subjective nature of evaluation that challenges the concept of trait structure, along with the validity and reliability of factor analysis (Butt, 2012).
It would appear that the objectivity of trait theory comes into question and therefore the methods it employs. The argument of patterns of similarity verses uniqueness and the approaches they adopt either nomothetic (universally general) or idiographic (individually unique) is a relevant area, as individual differences has traditionally set out to identify the universal dimensions of individuals. Eysenck used the nomothetic approach of factor analysis, which correlates clusters of traits that have been established through the use of subjective questionnaires and ratings. He addresses the criticism that factor analysis is prone to unreliable incongruent practitioner results stating that ‘universal agreement and correlation is strong support for his statistical method’ (Eysenck and Stanley, as cited in Butt, 2012, p. 51).
His measurement techniques provide objective data that can be used to draw comparisons across wide populations and provide a structure in which categorical typology can be conducted. However his factor analysis would appear to be used more in marketing and ‘occupational rather than clinical psychology’ (Butt, 2012). Mischel stated ‘that the only thing objective about personality inventories was their administration and scoring’ (Butt, 2004). Alternatively the idiographic data gathered by personal construct theory produces subjective results that can not be generalised and therefore applied to our understanding of traits or people as a whole (Butt, 2012).
Mischel concluded that personality testing only produces self-concepts and personal concepts and more appropriate idiographic measures should be employed like Kelly’s (1955) repertory grid, which helps to assess an individuals personal constructs. The repertory grid was devised by Kelly to elicit how individuals categorise constructs by comparing and contrasting experiences and events, allowing participants to access and assess personal meanings through construing. Individuals construe others behaviour in terms of their own subjective viewpoint. The results produced by repertory grid, can be subjected to factor or cluster analysis but only in terms of the individual meaning rather than a universal interpretation similar to Eysenck’s. Salmon (as cited in, Butt 2012) adopted Kelly’s theories of individual differences and integrates his philosophy and methods into learning in schools. She criticises the ‘market model of education’, which she states ‘delivers packages of knowledge’ that measures and classifies children through tests and examinations, which removes the ‘individuality of the individual’, creating hierarchies of ability.
Like Kelly she argues that learning should be more interactive and intersubjective, that children need to engage in debate in order to formulate and challenge their own implicit constructs. She believed that it is only by the acknowledgment of existing constructs that personal development can occur, through methods such as Kelly’s repertory grid. By adopting personal construct philosophy, she developed the Salmon line, which seeks to draw out the implicit by empowering students to define the idiosyncratic meaning of their personal expectations around academic progress. Salmon believed that the use of these phenomenological methods instead of the generalised preset formats of trait theory, offered access to ‘living material’ of understanding, which encourages learning and change. (Salmon1994, as cited in Butt 2012, p. 59)
Salmon also highlights the hierarchical nature of learning, that educational success is based on the testing and grading students through examinations. From a Kelliyan philosophy, hierarchical structures are unbeneficial; his emphasis is on the understanding of objects rather than labelling or comparison. Hierachical structures raise the issue of power relations that Kelly points to within trait theory and most psychometric methods. As with learning environments, power can be exerted by those who administer measurement tools and how they exert the knowledge that is gained. Trait theory because of its diagnostic emphasis has been criticised due to the pathologising nature of negative diagnosis. Richards (2002) highlights ‘reification where methodology ascribes an unwarranted description to an individual or object’ (p. 254). It could be argued that personal construct methods such as the repertory grid and the Salmon line eliminate the labelling of individuals by traits, by assisting them to identify their own personal constructs and meanings and therefore avoiding power relations (Butt, 2012).
Hollway (2012) highlights the importance of agency-structure dualism when considering experimental methodology. Eysenck’s proposes that traits have their explanations in innate biological factors, which would suggest that agency has little or no influence on behaviour and that social factors are irrelevant, suggesting that personality is fixed. Personal construct theory views this dualism as complimentary, where the individual is viewed in the context of the societal environment in which they are constructed. Kelly proposes that individuals have some degree of agency because structure partly restricts through social construction and therefore have an ability to initiate change.
While individuals can change their social and individual constructs, social structure clearly has an influence on behaviour. Salmon shows through examples of learning and the application of the salmon line, the interaction between agency and structure. She highlighted that ‘knowledge is never neutral it comes with the interests and concerns of a particular siociocultural source’ (Salmon, as cited in Butt, 2012, p. 59), clearly indicating how societal influences impact on the agency of individuals (Butt, 2012).
Both trait theory and personal construct theory seek to gain an understanding and explain why individuals act in terms of individual differences. Eysenck and Rachman’s trait theory adopts a nomothetic approach using psychometric testing to measure personality traits. Kelly’s personal construct theory emphasise the uniqueness of individuals, seeking to understand how individuals construct their subjective world views, based on their own experiences. Using phenomenological methods they produce detailed accounts of individual personalities that avoid comparisons, with an emphasis on interpretation rather than scientific explanation, in contrast to the psychometric tradition which sets out to discover societal norms and use these to explain individual differences (Butt, 2012).
Eysenck outlines personality in terms of dimensions which reflect the underlying biological basis of personality. Personal construct theory recognises the ability for change unlike trait theory and uses idiographic methods such as the repertory grid and the Salmon line to enable chance to occur, through the interaction of personal agency and social structures. Salmon showed how personal construct theory can be implemented into clinical practice, however a complete theory of personality would need to encompass, structure, psychopathology and change, it would appear that both theories have areas of development in both theory building and testing.
Butt, T. (2012). Individual differences In Hollway, W., Lucey, H., Phoenix, A., and Lewis, G. (eds). Social Psychology Matters (p.1-22). Milton Keynes: The Open University.
Butt, T. (2004). Understanding people, Basingstoke and New York, Palgrave MacMillan.
Richards, G. (2002). Putting psychology in its place, Hove, Psychology press.