Impulsivity: Four ways five factors are not basic to addiction

• Impulsivity is multifaceted, but debate continues as to the precise number of facets.
• Situation resembles debate between H. J. Eysenck and Costa & McCrae concerning personality structure.
• Strong evidence for unique role of two factors of impulsivity in addictive behavior, weak evidence for five factors
• Two-factor impulsivity models, anchored in biological processes, show remarkable consistency across domains.
• Consideration of biological evidence provides a necessary constraint on theory development.

Several impulsivity-related models have been applied to understanding the vulnerability to addiction. While there is a growing consensus that impulsivity is multifaceted, debate continues as to the precise number of facets and, more critically, which are most relevant to explaining the addiction-risk profile. In many ways, the current debate mirrors that which took place in the personality literature in the early 1990s (e.g., Eysenck's ‘Big Three’ versus Costa and McCrae's ‘Big Five’). Indeed, many elements of this debate are relevant to the current discussion of the role of impulsivity in addictive behavior. Specifically, 1) the use of factor analysis as an atheoretical ‘truth-grinding machine’; 2) whether additional facets add explanatory power over fewer; 3) the delineation of specific neurocognitive pathways from each facet to addictive behaviors, and; 4) the relative merit of ‘top-down’ versus ‘bottom-up’ approaches to the understanding of impulsivity. Ultimately, the utility of any model of impulsivity and addiction lies in its heuristic value and ability to integrate evidence from different levels of analysis. Here, we make the case that theoretically-driven, bottom-up models proposing two factors deliver the optimal balance of explanatory power, parsimony, and integration of evidence.