روابط بین تکانشگری عملکردی و ناکارآمد، تنزیل تاخیر و تحریف شناختی

Impulsivity is a multidimensional construct assessed by a variety of behavioural and self-report measures. Each measure is thought to assess a separate component, but the inter-relationship between these measures in relation to the functional and dysfunctional nature of this psychological construct remains unclear. In addition, cognitive attributes of functional and dysfunctional impulsivity have not yet been identified. The present study addressed these issues by examining the inter-relationships between impulsivity measured using the delay discounting task and self-report questionnaires, alongside a measure of cognitive distortions. The results showed that delay discount rates were positively correlated with both functional and dysfunctional impulsivity measures, non-planning-impulsiveness and total scores of the Barratt Impulsiveness Scale (BIS-11). These findings are consistent with the idea that discounting the value of delayed rewards may be related to some, not necessarily dysfunctional, forms of impulsive behaviour. Furthermore, the present study suggests that negative cognitive attributes may operate as cognitive processing associated with some subtypes of impulsivity, i.e., dysfunctional impulsivity, non-planning and cognitive impulsiveness.

Impulsivity is viewed as a prominent feature of many psychiatric disorders and has been assessed using a variety of behavioural and personality measures (e.g., Evenden, 1999, Mathias et al., 2002 and Webster and Jackson, 1997). These measures have helped us to consider impulsiveness as a personality construct encompassing behavioural, cognitive, emotional, and motor components that can vary across individuals. Most studies have focused on impulsiveness as a personality construct or behaviour which can be defined as an inability to wait, insensitivity to consequences, the tendency to act without forethought, an inability to inhibit inappropriate behaviours, and deficient tolerance of delay of gratification (e.g., Ainslie, 1975, Eysenck, 1993, Logue, 1995 and McCown and DeSimone, 1993). However, there are situations where such impulsive behaviours may have adaptive functions and others where impulsivity would be counter-productive. These definitions either fail to clearly distinguish between functional and dysfunctional aspects of impulsivity or only consider impulsivity as an abnormal personality trait. Dickman (1990) distinguished between two distinct and independent forms of impulsivity, i.e., functional impulsivity and dysfunctional impulsivity. According to Dickman’s model (Dickman, 1990), functional impulsivity is related to the tendency to take quick decisions when doing so is beneficial. In contrast, dysfunctional impulsivity is related to the tendency towards speedy and non-reflective decision-making despite the negative consequences of such actions. Accordingly, Dickman (1990) developed an inventory to discriminate these two forms of impulsive behaviour. Similarly, Eysenck (1997) distinguished between two distinct aspects of impulsiveness, one aligning with extraversion, i.e., extraverted impulsivity and the other with psychoticism, i.e., psychotic impulsivity. The former is the process of taking decisions with a calculated risk and a full awareness of the danger, while the latter is the process of taking decisions without any considerations of the associated risks or consequences of the action (Eysenck, 1997). Furthermore, Barratt and colleagues (Patton, Stanford, & Barratt, 1995) have developed a measure of impulsivity, which appears to measure impulsivity as an abnormal personality trait. The Barratt Impulsiveness Scale (BIS-11, Patton et al., 1995) has been validated in general psychiatric and normal populations as well as a group of male inmates from a maximum security prison unit. It measures three subtypes of impulsiveness: cognitive (attentional) impulsiveness (inattention and cognitive instability), motor impulsiveness (motor disinhibition), and non-planning impulsiveness (lack of self-control and intolerance of cognitive complexity) (Patton et al., 1995). Furthermore, Gray’s personality theory (1987) suggests that high impulsivity is associated with sensitivity to signals of reward due to the activity of the behavioural approach system (BAS) when such cues are encountered. One of the possible implications of this model is that individuals with high impulsivity may exhibit a lower tolerance for delayed rewards. In addition to self-report questionnaires, some studies have used behavioural measures to quantify a single index of impulsive behaviour. One of the most commonly used behavioural tasks to measure impulsive decision-making is Delay Discounting, which provides a valid and reliable measure of the value of delayed, relative to immediate rewards in both animal and human studies (Ainslie, 1974, Herrnstein, 1981, Logue, 1988, Mobini et al., 2002 and Richards et al., 1999). In delay discounting studies a key assumption is that the value of a reward is discounted as a function of the delay which precedes its delivery. Thus, delay discounting procedure often requires the subject to choose between a small immediate reward and a large delayed reward; in this case preference for the former is often considered as ‘impulsive’ and preference for the latter as ‘self-controlled’ (Logue, 1995, Mazur, 1987, Monterosso and Ainslie, 1999 and Rachlin, 1974). Some studies have examined the relationships between delay discounting as a behavioural measure and self-report questionnaires as personality measures of impulsivity and reported no such relationships (e.g., Lane et al., 2003, Mitchell, 1999, Reynolds et al., 2006 and White et al., 1994), whereas, some other studies have reported a positive correlation (e.g., Cherek et al., 1997, de Wit et al., 2007 and Kirby et al., 1999). A possible explanation for these discrepancies is that different self-report measures tap into different aspects of impulsivity in general, and that some of these components are captured by the delay-discounting task, while others do not. The present study therefore investigated the inter-relationship between delay discounting and different forms of impulsiveness measured both by the BIS-11 and Dickman’s measures of functional and dysfunctional impulsivity. An important further question would be whether people with high dysfunctional impulsivity discount the value of the delayed reward more rapidly than people with high functional impulsivity. To our knowledge no study has yet examined this question. This latter component of the study allows us to assess whether delay discounting represents a general feature of impulsivity, or better reflects an aspect of dysfunctional impulsivity. A second shortcoming in our understanding of the nature of impulsivity is the lack of information on the cognitive attributes which may contribute to impulsive behaviour. Hutchinson and colleagues (Hutchinson, Patock-Peckham, Cheong, & Nagoshi, 1998) found that measures of irrational beliefs and impulsiveness were moderately correlated in a group of students abusing alcohol. In another recent study, it was reported that ‘core beliefs’ related to ‘abandonment’ were positively associated with high levels of impulsive self-harming behaviour in a psychiatric population (Dench, Murray, & Waller, 2005). However, in these studies impulsivity was investigated alongside other psychological disorders, therefore, making it difficult to attribute the findings to impulsive behaviour. From a cognitive perspective, one of the questions open to more investigation is how individuals who score high on dysfunctional impulsivity relative to functional impulsivity interpret the events preceding such actions. Previously we reported that people with high impulsivity measured by the BIS-11 scored high on cognitive distortions suggesting that there might be some general and specific cognitive distortions associated with impulsive behaviour (see Mobini, Pearce, Grant, Mills, & Yeomans, 2006). More specifically, in the present study we aimed to investigate whether cognitive attributes of dysfunctional impulsivity differ from those of functional impulsivity. Taken together, the present study was designed to investigate (1) the inter-relationships between delay discounting with functional and dysfunctional impulsivity and also with cognitive, motor and non-planning impulsiveness; and (2) cognitive attributes associated with dysfunctional impulsivity vs. functional impulsivity, and discounting the value of the delayed rewards.

Table 1 shows Pearson’s correlation coefficients (r) between delay discounting (k), different subtypes of impulsivity measured by the self-report personality measures and cognitive distortions. The delay discounting (k) values were significantly correlated with both functional (r = 0.19, p < 0.05) and dysfunctional impulsivity scores (r = 0.21, p < 0.01) as well as the total impulsivity scores of the DII (r = 0.20, p < 0.05). Also, the results showed that k values were positively correlated with non-planning impulsiveness subscale (r = 0.32, p < 0.01) of the BIS-11 and total impulsivity scores on this scale (r = 0.22, p < 0.01).