The mere physical presence of another person reduces human autonomic responses to aversive sounds

Abstract

Social animals show reduced physiological responses to aversive events if a conspecific is physically present. Although humans are innately social, it is unclear whether the mere physical presence of another person is sufficient to reduce human autonomic responses to aversive events. In our study, participants experienced aversive and neutral sounds alone (alone treatment) or with an unknown person that was physically present without providing active support. The present person was a member of the participants' ethnical group (ingroup treatment) or a different ethnical group (outgroup treatment), inspired by studies that have found an impact of similarity on social modulation effects. We measured skin conductance responses (SCRs) and collected subjective similarity and affect ratings. The mere presence of an ingroup or outgroup person significantly reduced SCRs to the aversive sounds compared with the alone condition, in particular in participants with high situational anxiety. Moreover, the effect was stronger if participants perceived the ingroup or outgroup person as dissimilar to themselves. Our results indicate that the mere presence of another person was sufficient to diminish autonomic responses to aversive events in humans, and thus verify the translational validity of basic social modulation effects across different species.

Keywords: anxiety; similarity; skin conductance responses; social modulation.

Figure 1.

(a) Grand-averaged SCRs to aversive sounds. The shaded area depicts the time window that was used for the statistical analyses. (b) Histogram displays the significant main effect of treatment (alone/ingroup/outgroup) on the SCRs during the sound presentation. The values of SCRs were transformed by log (x + 1) to correct for skewness. **p < 0.01, *p < 0.05.

Figure 2.

The social modulation effect is shaped by state anxiety and similarity. Because there were no significant differences between the ingroup and outgroup treatment groups, the results are shown pooled over the two social treatment groups. (a) Relationship between state anxiety and SCRs to aversive sounds. State anxiety increased the SCRs to aversive sounds in the alone treatment group, but not in the social treatment groups. (b) Relationship between perceived similarity and SCRs to aversive sounds. Low scores of perceived similarity of the other (i.e. high scores in dissimilarity) were related to a stronger reduction in SCRs to the aversive sound. The shaded areas indicate standard errors of the mean.

Figure 3.

Path analysis based on the data of the ingroup and outgroup treatment groups. Individual state anxiety scores were used as the predictor, perceived similarity as the mediator, SCRs to aversive sounds as the dependent variable, and treatment (ingroup versus outgroup) as a moderator variable. ***p < 0.001.