A delay-specific neural indicator corresponds to delay-discounting behavior for both gain and loss.

OBJECTIVES: Delay-discounting, wherein the subjective value for delayed gain or loss decreases, has been attracting much attention from the social sciences as well as neuroscience and has been suggested asbeing related to reward processing in the brain. As reported, the feedback-related negativity (FRN), an electrophysiological measure of reward processing, increased by delayed-monetary gain and ΔFRN, which is the difference in FRNs for loss and gain at a certain time point, had no significant correlation with delay-discounting for gain. Thus, although a delay for gain could affect FRN, it is unclear whether FRN capturing such a delay effect has a direct relationship with delay-discounting in both gain and loss domains. METHODS: In this study, we introduced a delay-specific indicator, ΔFRNdelay, that is, the difference between FRN with and without delays, and investigated its direct relationship during the doors task with the discounting rate measured by the delay-discounting task in both the gain and loss domains. RESULTS: We found that, for loss, the delay enhanced FRN, whereas no such effect was observed for gains, and that this indicator was significantly correlated with delay-discounting in both domains. CONCLUSIONS: To our knowledge, this study is the first to suggest that FRN is sensitive to the effects of delay in losses on reward processing and that the new indicator directly corresponds to changes in subjective value as measured by delay-discounting.

Quantitative Cross-Cultural Similarities and Differences in Social Discounting for Gains and Losses.

Social discounting is when resource allocation decreases as social distance increases. Studies fitting different quantitative models to social discounting data have shown that a q-exponential function based on Tsallis' statistics best fits loss data, whereas a hyperbolic power function best fits gain data. However, a social discounting sign effect, where losses are discounted less than equivalent gains, has not been consistently found. This study fit four different quantitative social discounting models to gain and loss data for 40 United States (US) participants. We compared quantitative model fits to previous studies collected with Japanese and German participants to determine if (1) different quantitative social discounting models best fit loss and gain data, (2) US participants discounted less gains than Japanese participants, but not losses, and (3) US participants showed the sign effect. Results showed that the q-exponential function and the hyperbolic power function best fit median loss and gain data, respectively. There were no significant absolute differences between cultures for gains or losses, and US participants showed a robust sign effect. While most results for US participants were consistent with previous data, future cross-cultural social discounting studies are needed that manipulate sign as well as reward magnitude to determine best quantitative model fits. Social discounting results are also discussed in relation to their application to important health behaviors such as smoking and obesity.

Transient nature of cooperation by pay-it-forward reciprocity.

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation.