In Exp. 1, participants also completed the distance preference task whereby they chose a preferred interpersonal distance from a pair of stimuli that differed only in distance. We examined SPE on interpersonal distance by comparing the preferred distance between the spray + and manage sessions. ANOVA on the preferred distance revealed a significant effect of treatment [spray + , spray control, material control, F(2,56) = , P < 0.001, ?p 2 = 0.319; Fig. 1C]. The preferred distance was shorter in the spray + session than in the spray control [t(28) = ?4.241, P < 0.001, Cohen d? = 0.787] and material control sessions [t(28)=–4.172, P < 0.001, Cohen d? = 0.774]. The SPE on the preferred distance was replicated in Exp. 2 [t(30) = ?2.067, P = 0.047, Cohen d? = 0.371; Fig. 1D]. The analysis of percentage of choosing closer distance showed similar patterns of SPE in Exp. 1 and Exp. 2 (SI Appendix, Section 6 and Fig. S2). These results demonstrated reliable SPE on increasing preference of closer interpersonal distance.
SPE on the Public Believe Mediated The Impact on Social Point Taste.
As social trust provides a basis of close interpersonal distance (36), we next examined whether SPE on the preferred distance arose from its effect of enhanced trust. To detect a moderate correlation (r = 0.4; ref. 37) between SPE on trust and on interpersonal distance with ? = 0.05 and 90% power, a sample size of 61 participants was needed (G*Power 3.1; ref .38). Thus, the correlation and mediation analyses were conducted on data collapsed over Exp. 1 and Exp. 2. First, we showed that the SPE on trust (trustspray + ? trustcontrol) was significantly correlated with the SPE on preferred distance, i.e., spray + manipulation decreased preferred distance to a greater degree in individuals who showed stronger SPE on trust [r(60) = ?0.367, P = 0.004; Fig. 2]. A mediation analysis (SI Appendix, Section 7) further confirmed that the spray + manipulation impacted interpersonal distance through increasing social trust (Sobel test, Z = ?2.498, P = 0.012, partial mediation; Fig. 2 and SI Appendix, Fig. S3 and Tables S2 and S3). A bias-corrected bootstrap resampling analysis (5,000 resamples) of the effect size indicated that the mediator effect was different from zero with 95% confidence.
Placebo treatment increased preferences of closer interpersonal distance through increasing trust in others (*P < 0.05, **P < 0.01, and ***P < 0.001).
Placebo Medication Faster Interpersonal Ranges during the Real-Life Personal Correspondence.
Exp. 1 and Exp. 2 revealed SPE on individuals’ preference of projected social distance; however, choosing closer projected distance does not necessarily predict interpersonal distance in a real-life situation as a result of potential increases of anxiety (26, 27). We next examined SPE in a real-life situation (Exp. 3) in an adapted stop-distance task that measures real-life interpersonal distance and reflects the willingness to approach others (25 ? –27). In each session, a different female experimenter was instructed to move along the line toward the participant at a natural gait. Similar to previous work (39), participants were asked to determine a distance at which they felt very uncomfortable to interact with this first-met female, respectively, when there was or was not eye contact (as eye contact signals social motivation and has been shown to play an important role in real-life social interaction; ref. 40). We conducted a 2 (treatment, spray + vs. material control) ? 2 (eye-contact, with vs. without) ANOVA of the distance (log10 transformed; SI Appendix, Section 8 and Fig. S4). A significant main effect of eye-contact [F(1,29) = 9.646, P = 0.004, ?p 2 = 0.250] suggested longer distance from the female experimenter with vs. without eye contact. The main effect of treatment was significant [F(1,29) = 4.312, P = 0.047, ?p 2 = 0.129], as, relative to material control, spray + manipulation decreased interpersonal distance. Interestingly, a significant treatment ? eye-contact interaction [F(1,29) = 4 firstmet app.515, P = 0.042, ?p 2 = 0.135; Fig. 3A] indicated modulation of eye contact on the SPE on decreasing real-life interpersonal distance. Specifically, participants kept a closer distance with the female experimenter in the spray + session (relative to control) in the no-eye contact situation [t(29) = ?2.302, P = 0.029, Cohen d? = 0.420], but not the eye-contact situation [t(29) = ?1.210, P = 0.236, Cohen d? = 0.221]. These results indicated SPE on facilitating approach behavior, especially when eye contact was not involved.