To trust or not to trust: a thermal imaging study on the effects of social exclusion

While emotion regulation seems to be well understood in the individual domain, information about the inherent link between emotion regulation and social contexts is lacking. In this study, we investigated the behavioral and physiological consequences of social exclusion in control participants (n = 16) and in patients (n = 16) with psoriasis, a skin disease known to be often accompanied with emotion regulation deficits. Firstly, participants faced the social induction phase by playing the Cyberball Game in which they were excluded or included by other players. Then participants played the Trust Game (TG) in the role of investor. All participants took part in both exclusion and inclusion social inductions and played the TG twice. In the TG, the investor has to decide how much of € 10 to invest on familiar and unfamiliar players. The familiar (bad vs. good) players were the same players previously encountered in the Cyberball Game. Participants’ face temperature (peri-orbital region) during the task was measured by means of functional Infrared Thermal Imaging (fITI). Face temperature in this area is known to reflect the activation of the sympathetic system. We tested whether the social inclusion vs. exclusion affected participants’ trust toward other players by entering mean investments into a Repeated Measures 2 (social induction: exclusion, inclusion) × 2 (player: familiar, unfamiliar) ANOVA. We found a statistically significant social induction × player interaction (F [1, 31] = 4.78, p < .04). A post hoc LSD test showed that unfamiliar players were trusted significantly more after the social exclusion phase respect to the inclusion one (p < .02); in fact, after social inclusion, participants tended to trust more familiar participants respect to the unfamiliar ones (p < .09). A linear regression was calculated to predict a behavioral index (i.e. the differential investment on familiar minus unfamiliar players) based on mean peri-orbital temperature during social exclusion induction. A significant regression equation was found (F [1, 31] = 7.16, p < .012, R2 = .20), suggesting that the higher the activation of the sympathetic system during social exclusion, the more participants tended to trust the unfamiliar with respect to the familiar players who previously excluded them. Interestingly, a correlation analysis showed that the behavioral adjustments triggered by peri-orbital temperature increase during social exclusion were present only in the control group (r = .535, p < .05), while patients’ decisions were not influenced by temperature change (r = .29, p = .27). This result suggests that sympathetic activation during painful social interactions is pivotal in order to learn whether to trust others and to adjust future behavior consequently. This mechanism is probably deficient in patients with emotion regulation deficits.