Descriptive weaknesses in trait theory
Although there appears to be growing agreement among psychologists over the number, character and stability of personality dimensions (Deary & Matthews, 1993), trait theory’s description of personality is not always parsimonious and can be likened to ‘parts of an elephant described by a blind man’ (Costa & McCrae, 1996). This difficulty to obtain a complete understanding of any one whole person could also apply to other nomothetic approaches to personality description.
Trait theory explanations of personality
Trait theory allows for several explanations of personality, which in itself might indicate some conceptual vulnerability or may be deemed to reflect the complexity of personality as a concept. Hjelle & Ziegler (1992) anticipate that ‘the field of personality will probably always be more comprehensive than any single theory can encompass’. The explanations include genetic origins, biological functioning, and environmental and social influences as causes of individual differences on various personality dimensions.
Evaluation of trait theory explanations
Kline (1993) highlights the need for a clear link between description and explanation of personality dimensions, ‘it is difficult to argue that a factor is some kind of statistical artefact or that it is simply a group of semantically similar items if there is a relatively large heritability index’. The contribution of genetics to personality dimensions has been tested (Plomin et al, 1990) by comparing correlations on all ‘big five’ factors for identical and fraternal twins reared together and reared apart. The strongest positive correlations were found for identical twins reared together (N=0.41, E=0.54, O=0.51, A=0.47, C=0.41). However the next strongest correlations were for identical twins reared separately on factors of Extraversion, Neuroticism and Openness (N=0.25, E=0.30, O=0.43). While the data indicate divergent heritabilities for different factors, the genetic contribution (through the identical genetic make-up of the monozygotic twins) to personality over and above the environmental contribution (through separate rearing) is evident. Plomin et al (1990) estimate that, proportionally, genetics contributes 40% of personality derivation, with environment and error accounting for the remaining 40% and 20% respectively.
Eysenck (1967) explained individual personality differences as arising from neurophysiological differences. For example, an individual’s level of Neuroticism is thought to be linked to how highly activated their limbic system becomes. This has been tested by measuring respiration, sweating, and heart rate, all linked to autonomic nervous system functioning (Eysenck, 1967). Deary and Matthews (1993) conclude that research on the biological bases of personality dimensions has produced few simple effects. But this is only to be expected as hypotheses are based on oversimplified ideas about the brain. The direct contribution of biological causes to individual differences may be matched by the indirect contribution of biology through an individual’s selection of (and adaptation to) environment and the modifying effect on personality.
The contribution of environment to differences in personality has been examined by Plomin et al (1990). In their fraternal and identical twin study, outlined above, environmental influence was shown by the lower correlations for identical twins raised in separate environments compared with those for identical twins raised in the same environment (+0.15 vs. +0.41 and +0.19 vs. +0.47 for Conscientiousness and Agreeableness respectively). Both dimensions can be viewed as comprised of interpersonal traits and thus more amenable to environmental influence.
This shows that interaction between an individual and their environment can lead to long term effects on personality, e.g. through social interaction and learning. A person may seek information which will support their beliefs about another individual’s personality, which in turn can elicit belief-congruent behaviour from that individual and in turn promote self-fulfilling expectations, e.g. aggressive children seek out challenging environments and expect others to be hostile, which may actually elicit hostile behaviour from those around them (Dodge, 1986, cited in Gleitman, 1999). The contribution of information-processing mechanisms on trait effects may highlight social learning as one explanation for personality change and development.
Weaknesses in Explanation of Personality
The evidence for a genetic and an environmental basis for personality traits appears to be strong. However, the complexity of causality (i.e. the multiplicity of interactions between genetics, environment, biology, social culture, learning, cognition and random chance errors) makes it difficult to produce evidence of either explanatory links or predictive patterns between traits and how an individual functions.
The focus of trait theory explanations on individual differences between people rather than on the total functioning of an individual hinders an effective explanation as to why an individual’s personality is characterised as it is or how it may change over time. Costa and McCrae (1996) admit that their FFM “does not explain how social roles are forged into a personal identity, or how the flow of behaviour is organised, or how attitudes are formed and changed.”
Conclusion
The impact of this nomothetic approach on the theory’s description of personality was noted above. However, its impact is less critical on the theory’s description than on its explanation of personality. With enough blind men, we could eventually compile a fairly accurate description of an elephant, albeit lacking any mention of colour. Thus, blind men’s descriptions of parts of an elephant are of some relevance. Probably more so than their explanations for its behaviour in the Indian jungle. Trait theory is thus better at describing than explaining personality.
References
McCrae, RR and Costa, PT (1996). Toward a New Generation of Personality Theories: Theoretical Contexts for the Five-Factor Model. In Wiggins, JS (Ed.) The Five Factor Model of Personality: Theoretical Perspectives New York: Guilford Press (Chapter 3, pp51-79).
Galton xxxxx in Pervin
Pervin, LA & John, OP (2001). Personality: Theory and Research. (8th ed.) New York: John Wiley (Ch 1 & 2, pp xx
Bond 1994, Church, Katigbak and Ryeer 1995 – in Pervin
Deary, IJ and Matthews, G (1993). Personality Traits. The Psychologist. Vol No xx pp 299-310
Hjelle, LA & Ziegler, DJ (1992). Personality Theories: Basic Assumptions, Research and Applications. (3rd ed). (Chapter 1 pp 24) New York: McGraw Hill
Kline, P (1993). Comments on “Personality traits are alive and well”. The Psychologist. Vol No xx p 304
Plomin et al (1990) - notes
Eysenck (1967) - notes
Dodge, KA (1986) A social information processing model of social competence in children. Perimutter, AM (Ed.) Minnesota Symposium on Child Psychology (Vol 18 pp 77-125) Hillsdale, New Jersey: Erlbaum
Gleitman, H, Fridlund, AJF & Reisberg, D (1999). Psychology (5th ed.) Ch 16 pp 669-710) New York: WW Norton
McCrae, RR and Costa, PT (1996). Toward a New Generation of Personality Theories: Theoretical Contexts for the Five-Factor Model. In Wiggins, JS (Ed.) The Five Factor Model of Personality: Theoretical Perspectives New York: Guilford Press (Chapter 3, pp51-79).
