Abstract
Social norms, business etiquette, and common courtesy often compel us to mask selfish intentions under the guise of friendliness. Discerning others’ true intentions has important implications for selecting partners in all circles of life—business, friendship, and love (Trivers, 1985). However, intentions cannot be measured directly. Moreover, people are not always sincere in their signaled intentions. Thus, we often rely on external cues such as facial expressions, body language, and vocal tone to determine if ostensibly cooperative cues are, in reality, veiled acts of deception (DePaulo & Morris, 2004; Ekman & Friesen, 1969). How good are we at recognizing what is lurking under the facade of a trusting face? In general, our proficiency in judging the authenticity of cooperative expressions often fares little better than chance (Belot, Bhaskar, & van de Ven, 2012; Bond & DePaulo, 2006). This research examined whether the neuropeptide oxytocin—known for its wide-ranging effects on social cognition and behavior (Meyer-Lindenberg, Domes, Kirsch, & Heinrichs, 2011)—influences individuals’ ability to discern between truth tellers and deceivers.
Previous studies have detailed the influence of oxytocin in social contexts (Meyer-Lindenberg et al., 2011); however, its role in the detection of social deception is still unknown. Exogenous administration of oxytocin in economic exchanges increases trust and social approach, an effect moderated by cooperative incentives and group membership (Declerck, Boone, & Kiyonari, 2010; De Dreu et al., 2010; Kosfeld, Heinrichs, Zak, Fischbacher, & Fehr, 2005; Mikolajczak et al., 2010). In social-recognition tasks, exogenous administration of oxytocin promotes gaze to the eye region, improves identification of expressed emotions, and increases perceptions of trustworthiness (Bartz, Zaki, Bolger, & Ochsner, 2011). These results raise the possibility that oxytocin facilitates attention to social signals, making them more salient and rewarding (Groppe et al., 2013). How these socioaffective effects translate to the complex context of discerning cooperative intentions is unclear. Interpreting trust-relevant signals involves integrating vocal tone and content with context-dependent intuitive assessments of facial expressions, body language, and other subtle nonverbal cues (Bond & DePaulo, 2006; DeSteno et al., 2012).
To clarify the role of oxytocin in this complex and dynamic context, we had subjects watch clips of TV-show contestants making voluntary and spontaneous proclamations of their trustworthiness in an adaptation of the prisoner’s dilemma in return for monetary rewards of up to several thousand dollars. Because contestants’ rewards were contingent on both their own and their partners’ decisions, contestants regularly attempted to elicit cooperative behavior by conveying seemingly trustworthy, yet potentially deceitful, intentions. Subjects received monetary compensation for accurately predicting which contestants did in fact cooperate and which did not.
Materials and Method
Eighty-four male university students (mean age = 25.33 years, SD = 2.41) participated in the study in return for monetary compensation, which consisted of a fixed show-up fee of 50 shekels (approximately $12.50) in addition to a performance-dependent amount of 10 shekels per accurate prediction. Subjects provided written consent, and the study protocol was approved by Israel’s Ministry of Health. Subjects were randomly assigned to one of two conditions in which they self-administered either 24 IU of oxytocin (Syntocinon spray; Novartis, Basel, Switzerland) or a placebo. The placebo included all the Syntocinon ingredients except for the active hormone. Subjects could not differentiate between oxytocin and the placebo (Fisher’s exact test, p > .58).
Forty min after self-administration of oxytocin or the placebo, subjects viewed four clips of the Friend or Foe? game show. Each clip depicted two contestants (counterbalanced for gender) engaging in nonbinding discussions prior to making decisions of “friend” (cooperation) or “foe” (defection). Clips were presented in a random order and were cut before contestants’ decisions were revealed. Subjects were asked to predict each contestant’s decision, resulting in a total of eight predictions. For more details, see Description of Friend or Foe? Video-Clip Pairings in the Supplemental Material.
Results and Discussion
Under oxytocin, subjects were less accurate than placebo at predicting contestant decisions (See Fig. 1)—oxytocin: M = 3.86, SD = 1.51; placebo: M = 4.67, SD = 1.41; t(82) = 2.54, p = .013. Further, only in the placebo condition were subjects able to accurately predict contestants’ decisions with a probability higher than chance—oxytocin: t(41) = −0.61, p > .5; placebo: t(41) = 3.07, p = .004. Poorer accuracy in the oxytocin condition did not result from subjects predicting “friend” decisions more frequently: Subjects who received oxytocin did not differ from those who received the placebo in the number of “friend” predictions—oxytocin: M = 4.24, SD = 1.25; placebo: M = 4.38, SD = 1.15; t(82) = 0.55, p > .5. Additional analysis ruled out the possibility that the effects of oxytocin were affected by contestant partners’ decisions, subjects’ beliefs about whether they had received oxytocin or the placebo, or differences in mood or interpersonal closeness (see Additional Analyses in the Supplemental Material).
Results: number of accurate predictions and of “friend” (vs. “foe”) predictions as a function of treatment condition. Error bars represent standard errors of the mean. The asterisk denotes a significant difference between conditions (p < .05). OT = oxytocin.
Rather than improving subjects’ inferences about others’ mental states, oxytocin impeded accurate assessments of trustworthiness in risky social exchanges. Oxytocin decreased prediction accuracy but did not increase predictions of cooperative behavior in general. A possible mechanism consistent with these results may be that oxytocin suppresses the attentional salience of negative social stimuli, resulting in lowered social vigilance and arousal (Ebitz, Watson, & Platt, 2013; Norman et al., 2011).
Reduced social vigilance could result in lowered sensitivity to cues divulging deception or in reduced motivation to detect deceptive signals. In primate models, exogenous administration of oxytocin decreases attention to negative stimuli, which reduces information about the immediate social context (Ebitz et al., 2013; Parr, Modi, Siebert, & Young, 2013). Mounting evidence has suggested that oxytocin may have similar effects on attention and behavior in humans. Oxytocin administration alters responses to unpleasant or threatening stimuli, suppressing cortisol reactivity (Heinrichs, Baumgartner, Kirschbaum, & Ehlert, 2003) and attenuating amygdala activation (Domes et al., 2007; Gamer, Zurowski, & Büchel, 2010; Kirsch et al., 2005; Petrovic, Kalisch, Singer, & Dolan, 2008), which inhibits key hubs of social vigilance and emotional arousal (Dandeneau, Baldwin, Baccus, Sakellaropoulo, & Pruessner, 2007; Davis & Whalen, 2001). Reduced vigilance could also account for previous findings on the prosocial effects of oxytocin, given that suppressing aversive responses could facilitate social approach (Evans, Shergill, & Averbeck, 2010; Radke, Roelofs, & De Bruijn, 2013) and subsequent trust-related behaviors. However, as the results of this study demonstrate, in contexts in which suspicion may be advantageous, reduced social vigilance may also impose significant costs. When mixed motives lurk under the veneer of a friendly face, oxytocin may hinder our ability to recognize that something is askew.
Footnotes
Acknowledgements
The authors would like to thank David Mankuta for support and Matan Zilkha, Atar Shiloh, Reut Zeiri, and Ofer Glicksohn for help in administering the experimental sessions.
Declaration of Conflicting Interests
The authors declared that they had no conflicts of interest with respect to their authorship or the publication of this article.
Funding
E. Winter wishes to thank the German-Israeli Research Foundation and Google for their financial support.
References
Supplementary Material
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