Date of Award

2007

Degree Type

Thesis

Degree Name

Bachelor of Arts Honours

School

School of Psychology and Social Sciences

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr. Chris Theunissen

Second Advisor

Dr Greg Dear

Abstract

Impulsivity is generally thought to refer to rapid, spontaneous and inappropriate behaviour. One causal view of impulsivity is that of executive inhibitory dyscontrol. Inhibitory control requires the suppression of an implicit or explicit response and may be assessed with laboratory behavioural tasks. Executive inhibition includes cognitive inhibition, interference control and behavioural inhibition. Impulsivity is frequently measured using self-report personality-based inventories. Investigations of the relationship between inhibitory control and impulsivity are uncommon. It is further proposed that there is a significant inverse relationship between a self-report measure of impulsivity (the Barratt Impulsiveness Scale) (Patton, Stanford, & Barratt, 1995) and a behavioural measure of motoric inhibitory control (Stop-Signal task) (Logan, 1994). The proposed study will employ a non-clinical cohort to examine this hypothesis. Inhibitory deficits have frequently been reported in clinical groups. It is unknown whether the same deficit underlies the personality trait of impulsivity in non-clinical adult populations. The current study investigated whether there is an association between self-reported trait impulsivity and inhibitory motor control. The stop-signal task was employed to examine the inhibitory performance of non-clinical adults. Participants were allocated to a high or low impulsivity group on the basis of their Barratt Impulsiveness Scale (BIS-11) scores. Those participants scoring in the top 25% (n = 18) and bottom 25% (n = 18) on the BIS-11, from a sample of73, were allocated to the high or low impulsive groups respectively. The stop-signal task employed a visual choice reaction time 'go' task and participants attempted to inhibit their responses to the 'go' task when an auditory 'stop' signal was heard. The findings indicate that there was no deficit in motor inhibition found for high-impulsives, nor did the groups differ on either the speed of their response, or the probability of inhibiting their response, to a 'stop' signal. However, there was a weak but non-significant correlation found supporting an association between motor impulsivity and stop-signal reaction time (r = .35, p = .06). In conclusion, the current study found only minor evidence that impulsivity in a non-clinical adult cohort is associated with poor inhibitory motor control.

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