Impulsive decision-making

Impulsivity is a highly heterogeneous umbrella term, subsuming various traits and behaviours. An important behavioural construct is impulsive decision-making, often measured as temporal discounting in intertemporal choices, i.e., the tendency to discount future rewards as a function of delay until receipt. While impulsivity and impulsive decision-making have been extensively studied, many research questions remain unanswered. First, given the heterogeneity of impulsivity, its psychometric structure needs to be examined further. Second, impulsive decision-making has been shown to be malleable using time framing. Specifically, the date/delay effect demonstrates that temporal discounting is reduced when time is displayed in terms of dates rather than delay units. However, the cognitive and neural mechanisms of this effect are unclear. Third, recent findings suggest that temporal discounting could be a transdiagnostic marker of multiple mental disorders. Yet, transdiagnostic studies on temporal discounting are scarce. <br> This dissertation therefore examined the topic of impulsivity as well as the malleability and transdiagnostic changes of impulsive decision-making across five empirical studies and two narrative reviews. In Study I, the structure of impulsivity was examined using confirmatory factor and network analyses of trait and intertemporal choice measures. In Studies II and III, the cognitive and neural mechanisms of the date/delay effect were investigated using eye-tracking and functional magnetic resonance imaging (fMRI). In Studies IV and V, dimensional approaches to mental disorders were used to test associations between temporal discounting, the date/delay effect and schizotypy as well as a broader range of psychopathological dimensions. Finally, in Reviews I and II, the literature on individual differences and time perception in intertemporal choice was summarised. <br> Taken together, the studies and reviews confirmed the heterogeneous nature of impulsivity, detecting low yet significant correlations between most measures. The findings challenge the previously postulated separability of positive and negative urgency and suggest that lack of premeditation is central within the trait impulsivity network (Study I). Moreover, the date/delay effect was consistently replicated (Studies II–V). Compared to the delay condition, the date condition was associated with longer fixation times on and more saccades between time attributes as well as higher activation of brain regions relevant to episodic processing. This indicates that time perception differs in the two conditions (Studies II–III). Finally, whilst results on the association between schizotypy and temporal discounting were ambiguous, transdiagnostic dimensions reflecting anxiety/depression and inattention/impulsivity/overactivity were positively associated with temporal discounting. The date/delay effect was particularly effective in people scoring higher on positive schizotypy and the inattention/impulsivity/overactivity dimension (Studies IV–V). Overall, the findings give insights into the heterogeneous nature of impulsivity, the robustness and mechanisms of the date/delay effect and the transdiagnostic role of temporal discounting.