Activation of the reward system during sympathetic concern is mediated by two types of empathy in a familiarity-dependent manner

Abstract

Humans work to improve the situation of others through sympathetic concern. The empathic joy hypothesis proposes that the urge to help is stimulated by enhanced sensitivity to vicarious joy achieved through helping a recipient to meet their needs. We further hypothesized that the positive feeling-related brain activation that occurs in the striatum during sympathetic concern is enhanced by empathy in a familiarity-dependent manner. To test this, we conducted behavioral and functional magnetic resonance imaging experiments in which two participants simultaneously played a virtual ball-toss game where either the subjects' partner or an unfamiliar player was isolated by the other players. The subjects showed sympathetic behavior by tossing the ball to the isolated player and reported enhancement of self-positive feelings and anticipation of feeling improvements of the isolated player during sympathetic behaviors. Activation in the bilateral dorsal striatum became more prominent during the behaviors, supporting the empathic joy hypothesis. Dorsal striatal activity when helping a romantic partner positively correlated with affective empathic traits toward that partner, whereas the activity measured when helping a stranger positively correlated with perspective-taking traits. The correlation results further revealed a familiarity-dependent empathic enhancement of positive feelings. Therefore, sympathetic concern is invoked through empathic positive feeling.

Keywords:

• Affective empathy
• Cognitive empathy
• Positive feeling
• Sympathetic concern

Acknowledgments

We thank A.T. Sasaki, M. Matsunaga, K. Yoshihara, T. Koike, K. Makita, S.K. Sugawara, Y. Yoshida, E. Nakagawa, K. Shimada, and Y. Okamoto for experimental assistance, and R. Kitada and M. Miyahara for comments on this article. This study was partly supported by Scientific Research on Innovative Areas grants no. 23101507 (H.K.) and no. 22101007 (H.C.T.) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT), by a Grant-in-Aid for Scientific Research (S) no. 21220005 (N.S.), by a Grant-in-Aid for Young Scientists (B) no. 23700505 (H.K.), and by a Challenging Exploratory Research grant no. 23650224 (H.C.T.) from the Japan Society for the Promotion of Science. Part of this study was supported by “Development of biomarker candidates for social behavior,” carried out under the Strategic Research Program for Brain Sciences of MEXT.

H.K. designed and conducted the experiments, analyzed the fMRI data, and wrote this article. H.C.T. participated in the experimental design and conducted the experiments. H.K.T. helped to run the experiments. N.S. supervised the overall project and edited this article.