Integrating behavioral economics and behavioral genetics: delayed reward discounting as an endophenotype for addictive disorders. MacKillop James Journal of the experimental analysis of behavior Delayed reward discounting is a behavioral economic index of impulsivity, referring to how much an individual devalues a reward based on its delay in time. As a behavioral process that varies considerably across individuals, delay discounting has been studied extensively as a model for self-control, both in the general population and in clinical samples. There is growing interest in genetic influences on discounting and, in particular, the prospect of discounting as an endophenotype for addictive disorders (i.e., a heritable mechanism partially responsible for conferring genetic risk). This review assembles and critiques the evidence supporting this hypothesis. Via numerous cross-sectional studies and a small number of longitudinal studies, there is considerable evidence that impulsive discounting is associated with addictive behavior and appears to play an etiological role. Moreover, there is increasing evidence from diverse methodologies that impulsive delay discounting is temporally stable, heritable, and that elevated levels are present in nonaffected family members. These findings suggest that impulsive discounting meets the criteria for being considered an endophenotype. In addition, recent findings suggest that genetic variation related to dopamine neurotransmission is significantly associated with variability in discounting preferences. A significant caveat, however, is that the literature is modest in some domains and, in others, not all the findings have been supportive or consistent. In addition, important methodological considerations are necessary in future studies. Taken together, although not definitive, there is accumulating support for the hypothesis of impulsive discounting as an endophenotype for addictive behavior and a need for further systematic investigation. 10.1002/jeab.4

The value of emotion: how does episodic prospection modulate delay discounting? Liu Lei,Feng Tingyong,Chen Jing,Li Hong PloS one BACKGROUND:Humans often show impatience when making intertemporal choice for monetary rewards, preferring small rewards delivered immediately to larger rewards delivered after a delay, which reflects a fundamental psychological principle: delay discounting. However, we propose that episodic prospection humans can vividly envisage exerts a strong and broad influence on individuals' delay discounting. Specifically, episodic prospection may affect individuals' intertemporal choice by the negative or positive emotion of prospection. METHODOLOGY/PRINCIPAL FINDINGS:The present study explored how episodic prospection modulated delay discounting by emotion. Study 1 showed that participants were more inclined to choose the delayed but larger rewards when they imaged positive future events than when they did not image events; Study 2 showed that participants were more inclined to choose the immediate but smaller rewards when they imaged negative future events than when they did not image events; In contrast, study 3 showed that choice preferences of participants when they imaged neutral future events were the same as when they did not image events. CONCLUSIONS/SIGNIFICANCE:By manipulating the emotion valence of episodic prospection, our findings suggested that positive emotion made individuals tend to choose delayed rewards, while negative emotion made individuals tend to choose immediate rewards. Only imaging events with neutral emotion did not affect individuals' choice preference. Thus, the valence of imaged future events' emotion might play an important role in individuals' intertemporal choice. It is possible that the valence of emotion may affect the changed direction (promote or inhibit) of individuals' delay discounting, while the ability to image future events affects the changed degree of individuals' delay discounting. 10.1371/journal.pone.0081717