Social discounting involves modulation of neural value signals by temporoparietal junction.

Most people are generous, but not toward everyone alike: generosity usually declines with social distance between individuals, a phenomenon called social discounting. Despite the pervasiveness of social discounting, social distance between actors has been surprisingly neglected in economic theory and neuroscientific research. We used functional magnetic resonance imaging (fMRI) to study the neural basis of this process to understand the neural underpinnings of social decision making. Participants chose between selfish and generous alternatives, yielding either a large reward for the participant alone, or smaller rewards for the participant and another individual at a particular social distance. We found that generous choices engaged the temporoparietal junction (TPJ). In particular, the TPJ activity was scaled to the social-distance-dependent conflict between selfish and generous motives during prosocial choice, consistent with ideas that the TPJ promotes generosity by facilitating overcoming egoism bias. Based on functional coupling data, we propose and provide evidence for a biologically plausible neural model according to which the TPJ supports social discounting by modulating basic neural value signals in the ventromedial prefrontal cortex to incorporate social-distance-dependent other-regarding preferences into an otherwise exclusively own-reward value representation.

Gender-Specific Effects of Cognitive Load on Social Discounting.

We live busy, social lives, and meeting the challenges of our complex environments puts strain on our cognitive systems. However, cognitive resources are limited. It is unclear how cognitive load affects social decision making. Previous findings on the effects of cognitive load on other-regarding preferences have been ambiguous, allowing no coherent opinion whether cognitive load increases, decreases or does not affect prosocial considerations. Here, we suggest that social distance between individuals modulates whether generosity towards a recipient increases or decreases under cognitive load conditions. Participants played a financial social discounting task with several recipients at variable social distance levels. In this task, they could choose between generous alternatives, yielding medium financial rewards for the participant and recipient at variable social distances, or between a selfish alternative, yielding larger rewards for the participant alone. We show that the social discount function of male participants was significantly flattened under high cognitive load conditions, suggesting they distinguished less between socially close and socially distant recipients. Unexpectedly, the cognitive-load effect on social discounting was gender-specific: while social discounting was strongly dependent on cognitive load in men, women were nearly unaffected by cognitive load manipulations. We suggest that cognitive load leads men, but not women to simplify the decision problem by neglecting the social distance information. We consider our study a good starting point for further experiments exploring the role of gender in prosocial choice.

Brain stimulation reveals crucial role of overcoming self-centeredness in self-control.

Neurobiological models of self-control predominantly focus on the role of prefrontal brain mechanisms involved in emotion regulation and impulse control. We provide evidence for an entirely different neural mechanism that promotes self-control by overcoming bias for the present self, a mechanism previously thought to be mainly important for interpersonal decision-making. In two separate studies, we show that disruptive transcranial magnetic stimulation (TMS) of the temporo-parietal junction-a brain region involved in overcoming one's self-centered perspective-increases the discounting of delayed and prosocial rewards. This effect of TMS on temporal and social discounting is accompanied by deficits in perspective-taking and does not reflect altered spatial reorienting and number recognition. Our findings substantiate a fundamental commonality between the domains of self-control and social decision-making and highlight a novel aspect of the neurocognitive processes involved in self-control.

Exogenous cortisol causes a shift from deliberative to intuitive thinking.

People often rely on intuitive judgments at the expense of deliberate reasoning, but what determines the dominance of intuition over deliberation is not well understood. Here, we employed a psychopharmacological approach to unravel the role of two major endocrine stress mediators, cortisol and noradrenaline, in cognitive reasoning. Healthy participants received placebo, cortisol (hydrocortisone) and/or yohimbine, a drug that increases noradrenergic stimulation, before performing the cognitive reflection test (CRT). We found that cortisol impaired performance in the CRT by biasing responses toward intuitive, but incorrect answers. Elevated stimulation of the noradrenergic system, however, had no effect. We interpret our results in the context of the dual systems theory of judgment and decision making. We propose that cortisol causes a shift from deliberate, reflective cognition toward automatic, reflexive information processing.