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 jet + and handle 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 into the Public Believe Mediated The Affect Interpersonal Length Preference.
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 Therapy Quicker Interpersonal Distances from inside the Real-Existence Social Interaction.
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) = 4.515, 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 farmers dating site 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.