Abstract
The research reported in this dissertation supports a conceptualisation of impulsivity as a fundamental trait which is not subsumed by other traits in large scale models of personality, whether of three five or more factors. It argues for this by showing that a measure of impulsivity demonstrates incremental validity over and above the validity of two measures of the Big Five personality traits in the prediction of a variety of behaviours which previous research has linked to individual differences in impulsivity. The research also demonstrates that while impulsivity is a coherent trait it nevertheless subsumes at least two and perhaps three correlated lower order traits; in the first instance this is demonstrated through an analysis of the factor structure of the BIS-11 which replicates the factor structure proposed by Patton et al (1996). Research reviewed in the first three chapters suggests a conceptual overlap between the multi-facetted trait of impulsivity and the dual factor model of inattentive and impulsive behaviours which constitutes the syndrome of ADHD. Two studies explore this overlap by first establishing that ADHD behaviours may be considered as two highly correlated traits and then exploring the correlations and conceptual overlap between these ADHD traits and the impulsivity facets measured by the BIS-11. The results suggest that while the correspondence between the variables across the two questionnaires and domains is not simple it does justify further exploration. The final study explores the relationships between self report measures of inattention and impulsivity and laboratory tasks selected to tap into behavioural and cognitive inhibition. The significant correlation between the cognitive inhibition tasks and the variance shared by the inattention and impulsivity scales supports the hypothesised role of cognitive variables in affecting individual differences in a unitary construct of impulsivity/inattention.