Associations between laboratory measures of executive inhibitory control and self-reported impulsivity

Abstract

Personality measures of maladaptive behavior often target the notion of impulsivity, which broadly refers to rapid and ill-considered conduct. The underlying cause of impulsive behavior, however, is not well understood, and there are many conflicting results. It has been suggested that impulsivity arises from inhibitory dyscontrol, a neuropsychological notion that is assessed via behavioral measures. We conducted a preliminary investigation of the association between a common self-report measure of impulsivity, the Barratt Impulsiveness Scale, and four behavioral paradigms of inhibitory control (motor inhibition, stop signal, Stroop, and negative priming) in normal adults (n = 31; age range: 19–51). Stroop conflict correlated significantly with non-planning, attentional, motor, and overall self-reported impulsiveness; motor disinhibition correlated significantly with non-planning impulsiveness; and response variability was associated with motor impulsiveness. Thus, there is evidence to suggest that, among normal adults, impulsivity is associated with some specific measures of inhibitory dyscontrol.

Introduction

Impulsivity is characterized by rapid, unplanned, inappropriate, and potentially maladaptive conduct (e.g., Visser, Das-Smaal, & Kwakman, 1996). It is observed in both clinical and non-clinical populations, and most commonly measured using self-report personality inventories. Despite variability in the behavioral expression of impulsiveness (ranging from, for example, a disinhibited verbal response to severe risk-taking and aggression), there is agreement on the general characteristics of impulsive behavior. Investigations of impulsivity, however, are limited by an imprecise understanding of the underlying cognitive cause of such behavior. A possible underlying cause of impulsivity is inhibitory dyscontrol.

Inhibitory control concerns the suppression of an explicit or implicit response. It is suggested that inhibitory control is governed by the orbitofrontal cortex (Fassbender et al., 2004); it is likely, however, that several reciprocally connected cortical and subcortical structures are involved (Bradshaw, 2001).

Paradigms of inhibition reflect an array of putative abilities. Nigg (2000) identifies “executive inhibition” (p. 237), which includes interference control, cognitive inhibition, and behavioral inhibition. Logan, Schachar, and Tannock (1997) suggest that executive inhibitory dyscontrol underlies impulsivity. This relationship is implied by several explanatory models, the most common of which maintains that inhibitory dyscontrol of an inappropriate response produces impulsive behavior, as in the case of impulsive violence. Barkley (1997) suggests that inhibitory control provides a delay in which executive functions can operate effectively. At present, however, few researchers have examined the relationship between impulsivity and inhibitory control.

Impulsivity is often measured via self-report (i.e., personality-based impulsivity). Laboratory based inhibitory control tasks (often considered objective tests of impulsivity) provide a measure that is uninfluenced by an individual’s biases and inaccuracies. Laboratory tasks, however, are usually administered in a relatively neutral environment, and do not account for factors that mediate impulsivity (e.g., autonomic arousal). This is where self-report measures, despite their limitations, may possibly come into their own. If we are to use both methods, an important conceptual question concerns the (putative) association between scores based on ‘objective’ laboratory measures of inhibition and scores derived from self-report tools such as questionnaires.

Impulsivity and inhibitory control have been examined in a range of clinical and non-clinical populations (see Evenden, 1999). Results traditionally suggest that personality measures of impulsivity inter-correlate well, but poorly with measures of inhibitory control (e.g., Milich and Kramer, 1984, White et al., 1994). It is unclear whether the apparent lack of relationship represents the measurement of distinct and unrelated concepts, measurement error, or variability in the measures used.

By contrast, a small number of recent investigations suggest that inhibition and personality-based impulsivity may be (negatively) related. Logan et al. (1997) found an association between high-impulsivity on the Eysenck Personality Scale and poor stopping ability in university students, while Swann, Bjork, Moeller, and Dougherty (2002) found that response disinhibition on a continuous performance task correlated significantly with the Barratt Impulsiveness Scale. Concerning cognitive inhibition, Visser et al. (1996) found a diminished negative priming effect in children subjectively classified as “socially impulsive”, while Posner et al. (2002) found significant correlations between Stroop conflict and a self-report measure of behavioral control. Inconsistent findings are perhaps due to the measures employed; many older studies are limited by the use of measures which incorporate an inhibitory component, but are not pure measures of inhibition. Such measures are unduly affected by other processes, such as working memory.

The current study was designed as a preliminary investigation of the relationship between several laboratory measures of inhibition and a popular self-report measure of impulsivity in a normal adult population. This would allow us to determine whether there is evidence to suggest that reduced inhibitory control is associated with personality-based impulsivity in a non-clinical adult sample.