title: Non-reciprocal altruism may be attributable to hyperbolicity in social discounting function.
abstract: Humans show altruism even for chance acquaintances whom they will never meet again (non-reciprocal altruism). With respect to evolutionary and economic perspectives, reciprocal altruism is not actually puzzling, because reciprocal altruism maximizes subjects' benefit/fitness in the long run; while non-reciprocal (pure) altruism still presents a challenge to evolutionary biology and neuroeconomics. Understanding neuropsychological bases of non-reciprocal altruism/generosity for unrelated people is also important for neuropsychiatry, because several types of impulsive psychiatrics (e.g., social phobia, substance abusers, psychopaths) often have reduced altruism/generosity for other people, which is associated with their problematic/impulsive social behavior. Regarding the relationship between impulsivity and reciprocal altruism, it has been shown that subjects who are impulsive in intertemporal choice (having a large time-discounting rate) have low degrees of reciprocal altruism, which is in line with economic theories and neuropharmacologically treatable with serotonin/norepinephrine reuptake inhibitors. However, little is known regarding the relationship between non-reciprocal altruism and discounting behavior, and neuropsychological processing underlying the relationship. Recently, Jones and Rachlin reported that generosity for other individuals with different social distances follows a hyperbolic discounting function, which has been employed to describe inconsistent time-discounting. In this study, I propose that non-reciprocal (pure) altruism may be, at least partially, attributable to hyperbolicity of a social discounting function (inconsistency in "interpersonal choice"). Neuropsychological mechanisms underlying interpersonally-inconsistent social discounting and possible implications for neuropsychopharmacological treatments for impulsive psychiatrics' problematic social behavior are discussed.
authors.affiliation: Department of Cognitive and Behavioral Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan. taiki@ecs.c.u-tokyo.ac.jp
authors.forename: Taiki
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000533:Altruism; D002755:Choice Behavior; D003657:Decision Making; D006801:Humans; D007175:Impulsive Behavior / Q000503:physiopathology* / Q000523:psychology*; D008960:Models, Psychological; D012201:Reward; D012919:Social Behavior