British Academy: The UK's National Academy for the Humanities and Social Sciences
Dr Luke D Smillie
Dr Luke Smillie received a British Academy Postdoctoral Fellowship in 2006, which he held in Department of Psychology at Goldsmiths, University of London. He is currently researching individual differences, with a particular focus on a) biologically-informed perspectives on personality (especially extraversion and impulsivity-related traits), and b) individual differences in motivation, emotion and cognition, c) implications (e.g., human performance, psychopathology).
Dr Smillie presented a poster entitled 'Individual Differences in Reward-Reactivity' at the 2009 British Academy Postdoctoral Symposium.
INDIVIDUAL DIFFERENCES IN REWARD-REACTIVITY
Figure 1: Factor Loading Plot from psychometric study.
Extraversion (E) falls on the ‘Reward Reactivity’
dimension whilst Psychoticism (P) falls on the
‘Impulsivity’ dimension.
Figure 2: Variation in trait Extraversion according
to presence of theA1 allele of the DRD2 gene.
Figure 3: Feeback-Related-Negativity occurs over frontal
areas of the brain and has a negative peak at 200-300ms
post-stimulus.
Abstract
Dopamine functioning drives our biobehavioural reactions to reward, which has been argued to form the biological basis of the personality trait Extraversion, but which may also relate to trait Psychoticism (Pickering, 2004; Smillie & Pickering, 2008). I used psychometric, genetic and psychophysiological paradigms to compare Extraversion and Psychoticism in terms of their relationship with reward-reactivity and dopamine functioning.
1. Psychometric Study
Responses from 122 University students to several relevant personality measures, including Extraversion and Psychoticism from the Eysenck Personality Questionnaire (EPQ; Eysenck & Eysenck, 1991), were subjected to a factor analysis to determine psychometric structure. Results indicated these measures to form two orthogonal dimensions, apparently reflecting the constructs of ‘Reward Reactivity’ and ‘Impulsiveness’. Extraversion was subsumed by the Reward Reactivity factor and Psychoticism by the Impulsivity Factor (see Figure 1).
2. Genetic study
The EPQ was administered to 122 University students who also provided a ‘cheek-swab’ sample from which DNA could be extracted. DNA was genotyped for the Taq1A Polymorphism of the DRD2 gene, which has functional consequences for dopamine functioning. Analyses revealed a significant association between Extraversion and variation in the DRD2 gene; carriers of at least 1 copy of the ‘A1’ allele had slightly higher Extraversion scores than those without this mutation (see Figure 2; p = .03). Psychoticism was unrelated to variation in the DRD2 gene (p = .25).
3. Psychophysiological Study
Four equal-sized “extreme groups” (high/low Extraversion, high/low Psychoticism, total N = 48) of students participated in an associative learning task during which brain responses to reward (Event Related Potentials) were recorded using Electroencephalogram. Of interest was the component known as ‘Feeback-Related-Negativity’ (see Figure 3), which has a role in dopamine signalling (Holroyd & Coles, 2002). Preliminary analyses were inconclusive; further data collection is in progress.
Conclusion
Converging evidence suggests that Extraversion, not Psychoticism, is a trait manifestation of dopamine mediated reward-reactivity, but further research is needed.
Key reference
Smillie, L. D. (2008). What is reinforcement sensitivity? Neuroscience paradigms for approach-avoidance process theories of personality. European Journal of Personality, 22, 359-384. For further information visit www.paidresearch.org
