An Argument Against Dual Valuation System Competition: Cognitive Capacities Supporting Future Orientation Mediate Rather Than Compete With Visceral Motivations.

The dynamic inconsistency of preference is well documented in behavioral research, but its basis remains controversial. In this article, we summarize recent functional magnetic resonance imaging (fMRI) work in the domain of intertemporal choice, specifically considering evidence bearing on the hypothesis that delay discounting in humans is determined by competition between an evolutionarily older system that discounts precipitously with delay (System 1), and a newer system that exhibits very little discounting (System 2). We argue that neuroimaging evidence does not support the hypothesized separate and competing value systems. While it is clear that the sophisticated cognitive capacities that lead to greater valuation of larger later alternatives (e.g., selective attention and self-signaling) depend critically on neocortical structures, these capacities affect intertemporal choice through mediation of (rather than competition with) older cortical and subcortical structures central to reward and motivation. Taken together, neuroimaging evidence supports the alternative hypothesis that intertemporal choice is guided by a single valuation system.