Laboratory tasks are understood to measure variability in cognitive processes that can contribute to impulsive behavior. Parallel to the questionnaire-based literature, these efforts are complicated by the use of several different tasks that gauge different aspects of impulsivity. Organizational schemes provided by Friedman & Miyake (2004) and Dougherty and his colleagues (Dougherty, Marsh & Mathias 2002; Marsh et al. 2002; Dougherty et al. 2005a,b) suggest five different types of cognitive tasks. First, prepotent response inhibition, or the inability to inhibit an already initiated response, refer to ‘the ability to suppress dominant, automatic or prepotent responses.’ Second, resistance to distractor interference involves avoiding interference from task-irrelevant information in the external environment (Friedman & Miyake 2004), and third, resistance to proactive interference involves resisting memory intrusions of information previously, but no longer relevant to the task (Friedman & Miyake 2004). Fourth is the tendency not to delay responding in order to obtain a larger reward (Dougherty et al. 2005b). A tendency to prefer immediate over delayed rewards is considered to be an aspect of impulsivity that is potentially important to addiction, since
