International Journal of Neuropsychopharmacology (2014), 17, 1785–1792. doi:10.1017/S146114571400090X

© CINP 2014

ARTICLE

Oxytocin makes females, but not males, less forgiving following betrayal of trust Shuxia Yao, Weihua Zhao, Rui Cheng, Yayuan Geng, Lizhu Luo and Keith M. Kendrick Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China

Abstract Although oxytocin has been shown to enhance trust behavior, to date no study has directly established whether oxytocin can modulate the effect of repair strategies on restoring damaged trust. In the current double-blind, between-subjects, placebo-controlled design study, two repair strategies were used to examine the effect of intranasal oxytocin administration on modulating trust restoration in a revised trust game. The results showed that although oxytocin had no overall effect on modulating trust restoration, it did have a significant gender specific effect. Female subjects showed less evidence for trust repair in the oxytocin compared with the placebo treatment group. This suggests that oxytocin may make female subjects exhibit more punitive behavior towards partners who violate their trust and less sensitive to repair strategies provided by them. Interestingly, this gender specific effect was more evident in the context of attempted trust repair using financial compensation. However, it also extended to both apology alone and no compensation conditions, but not to the fair one, in females exhibiting high trait forgiveness. Thus females with a more forgiving attitude towards betrayal may actually be more likely to punish betrayal following oxytocin treatment. Received 24 March 2014; Reviewed 26 April 2014; Revised 28 April 2014; Accepted 2 May 2014; First published online 11 June 2014 Key words: Gender difference, oxytocin, trait forgiveness, trust repair.

Introduction As a social species, we have to interact with and cooperate with each other at individual, group and even national levels in order to survive. Trust is indispensable for optimal social interaction and co-operation and as such contributes significantly to social, economic and even political success (Zak and Knack, 2001). However, trust violation is also common during interactions and can be particularly harmful to individuals wanting to engage in future cooperation. It is, therefore, important to establish the extent to which trust can be restored after it has been violated in some way. Indeed, previous studies have shown that certain repair strategies, including financial compensation and apology, are effective in rebuilding the damaged trust (De Cremer, 2010; Desmet et al., 2011; Haesevoets et al., 2013; Schniter et al., 2013). A number of studies have shown that the hypothalamic neuropeptide, oxytocin (OXT) can enhance trust in economic game contexts. Using a trust game paradigm, Kosfeld et al. (2005) first demonstrated that OXT can enhance an individual’s trust behavior during interpersonal interactions. However, other research has

Address for correspondence: Dr Keith M. Kendrick, No. 4, Section 2, North Jianshe Road, Chengdu 610054, China. Tel.: +86-28-83201358 Fax: +86-28-83201358 Email: [email protected]

shown that OXT does not promote blind trust, since it does not have effects when clues are given indicating that a trustee is untrustworthy (Mikolajczak et al., 2010a). The enhancement effect of OXT on trust is also not limited to economic game contexts. Thus OXT treatment can increase ratings of trustworthiness for neutral expression faces (Theodoridou et al., 2009), and make subjects more trusting even when their personal confidential information is involved (Mikolajczak et al., 2010b). Several studies have also reported increases in peripheral OXT concentrations in different trust situations (Zak et al., 2005; Kéri and Kiss, 2011). These findings suggest a general facilitative role of OXT in promoting human trust. However, no study to date has investigated a potential modulatory effect of OXT on repair strategies in restoring damaged trust, although trust restoration is clearly vital for ensuring continued cooperation in many different contexts. Some previous studies are suggestive in this respect, with OXT being found to help maintain trust levels even after trust has been broken on several occasions (Baumgartner et al., 2008). Also, OXT has been shown to increase the tendency to attribute a trust betrayal to non-personal factors and impact on investment reduction after trust betrayal by mediating its interaction with angry rumination (Klackl et al., 2013). Based on the above previous findings, the main objective of the present study was to investigate whether OXT can modulate the effect of repair strategies on restoring

1786 S. Yao et al. damaged trust. OXT was administrated after trust betrayal to avoid its potential influence on trust enhancement per se, as originally demonstrated by Kosfeld et al. (2005). Two common repair strategies (financial compensation vs. apology) were used in a revised version of the trust game. We hypothesized that if OXT facilitates forgiveness of untrustworthy behavior then it should increase the impact of trust repair strategies. Method Participants 104 healthy students (57 male, mean age 21.2 years, S.D. = 1.76) from the University of Electronic Science and Technology of China participated in the study. None of the subjects were currently taking any form of medication and none reported having had a neurological problems or psychiatric illness. None of the female subjects were pregnant or taking oral contraceptives, but no attempt was made to test them at specific times of their menstrual cycle. 10 subjects (nine male; four in OXT group) were excluded due to their expressed disbelief of the existence of their partners (five subjects), or as a result of making identical responses across conditions (five subjects). All the subjects completed a number of questionnaires (Chinese versions) immediately prior to the experiment, including the General Trust Scale (GTS; M. Siegrist, C. Keller, T. C. Barle, and H. Gutscher, unpublished observations), Tendency to Forgive (TTF, Brown, 2003), Attitudes toward Forgiveness (ATF; Brown, 2003), Positive and Negative Affect Schedule (PANAS; Watson et al., 1988), Beck Depression Inventory (BDI-II; Beck et al., 1996), Self-Esteem Scale (SES; Rosenberg, 1965), State-Trait Anxiety Inventory (STAI; Spielberger et al., 1983) and The Empathy Quotient (EQ; Baron-Cohen and Wheelwright, 2004). The study was approved by the ethical committee of the University of Electronic Science and Technology of China and all subjects gave informed consent to take part. Procedure The study used a double-blind, between-subject, placebocontrolled design. For the experiment, subjects were first administered a single intranasal dose of 24IU OXT (Syntocinon Spray, Sichuan Meike Pharmacy Co. Ltd, China; three puffs of 4IU per nostril with 30 s between each puff) or PLC (also three puffs per nostril). The PLC treatment was also provided in the same type of dispenser bottle by the pharmaceutical supply company providing the OXT nasal spray, and contained all of the same ingredients other than the neuropeptide. In line with many previous reports (Striepens et al., 2011) the experimental paradigm started 45 min after OXT or PLC treatment, which is estimated to allow increased concentrations of the peptide to occur within the cerebrospinal fluid (Striepens et al., 2014). In post-experiment

interviews subjects were unable to identify better than chance whether they had received the OXT or PLC treatment. Subjects were asked to abstain from caffeine, alcohol and smoking at least 2 h prior to the experiment. Participants took part in a revised version of the trust game where there were five players involved (one trustor vs. four trustees). The participant always played the role of the trustor and the trustees were not real. Participants were told that they would play in an investment game with four different partners present in the laboratory next door, and that their role (trustor or trustee) was randomly assigned. They were further informed that they would not meet each other and that individual information would not be divulged either before or after the experiment. The task was implemented using e-prime and participants were seated in front of a 24 in computer display screen. In our revised trust game paradigm, the trustor was provided with an initial endowment of 12 monetary units (MU, 5 MU worth 1 RMB/yuan) and each trustee also got 12 MU. From their initial 12 MU, participants could choose 0, 4, 8, or 12 MU to invest in each partner and the investment would be tripled. As a result, the total MU of the trustee would increase. Subjects were encouraged not to invest 0 MU. The trustee then had the option to keep the entire MU or to give back some of their additional MU to the trustor to produce more equivalent gains for both trustor and trustee (Berg et al., 1995; Kosfeld et al., 2005; Baumgartner et al., 2008). Participants received feedback on the decisions of their individual partners after they had invested in all four of them. Among the four virtual trustees, three did not send back any MU to the participant, which was preprogrammed in order to induce trust betrayal. The remaining trustee sent back sufficient MU to result in equivalent incomes for both trustee and trustor (i.e. fair condition). The four trustees were assigned different surnames with their first names replaced by ‘**’. This allowed participants to discriminate which partner paid back their trust and which partner did not. The four most commonly used surnames in China were selected to reduce the chance of a possible name bias. The order and names of the fair and unfair trustees were counterbalanced across participants. The decisions ‘made’ by the trustees were sent to the trustor one by one before they were summarized on the display screen. Participants were then asked to complete a benevolence scale to rate the effect of trust violation (Mayer et al., 1995; De Cremer, 2004; Desmet et al., 2011). After having finished the scale, subjects were administered intranasal OXT or PLC. The next part of the experiment started 45 min after OXT or PLC treatment. At the end of this 45 min interval, subjects were informed that the experimenter had asked each of the trustees to think again about his/her decision and to communicate what he/she could do (see also De Cremer, 2010). Participants were further told that

Oxytocin decreases females’ trust after betrayal

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Table 1. Ages and questionnaire scores for subjects in OXT and PLC group (mean±S.E.M.) Measurements

Oxytocin

Placebo

Age (yr) General Trust Scale (GTS) Tendency to Forgive (TTF) Attitudes toward Forgiveness (ATF) Self-Esteem Scale (SES) Empathy Quotient (EQ) Beck Depression Inventory (BDI-II) State-Trait Anxiety Inventory (STAI)-State State-Trait Anxiety Inventory (STAI)-Trait Positive and Negative Affective Scale (PANAS) Positive Negative

21.5±0.3 32.4±0.6 16.5±0.6 29.4±0.5 31.9±0.6 36.1±1.3 8.2±1.2 38.5±1.3 39.6±1.2

21.1±0.2 32.0±0.5 15.5±0.5 29.8±0.5 32.3±0.5 34.8±1.3 9.5±0.9 40.0±1.3 41.7±1.2

1.32 0.51 1.30 −0.55 −0.56 0.72 −0.87 −0.82 −1.22

0.191 0.609 0.198 0.585 0.580 0.472 0.389 0.414 0.224

28.8±0.9 17.7±0.9

28.4±0.6 17.1±0.8

0.40 0.46

0.694 0.649

a

t-value

p-value

95% Confidence interval.

their partners’ decisions on this would be communicated to them via the program and no mention was made that there would be a further investment opportunity in a second round. The preprogrammed decisions were sent to paricipants one after another. In the financial compensation condition, the ‘trustee’ said: ‘I decide to give ** MU (i.e. this would make the incomes of the trustor and the trustee equal) back to you’; in the apology condition, the ‘trustee’ said: ‘I realize that my offer to you was not appropriate (i.e. taking responsibility) and I feel bad about this (i.e. expression of remorse)’ (De Cremer, 2010); in the fair condition and in the nothing condition, the ‘trustee’ said: ‘I decide to do nothing’. The apology format used was the same as in De Cremer (2010), and consisted of two necessary elements: (a) taking responsibility, and (b) expressing remorse based on Scher and Darley (1997). Next all the decisions ‘made’ by trustees in the first round, and the decisions after further communication, were summarized on one screen for the participant. Furthermore, the total amount of MU obtained by the trustor and each trustee were also presented following each decision. As a result, subjects could get a clear summary on the income comparison between themselves and their partners. After presentation of the feedback, subjects were asked to invest in their partners again in another round of the game. The past decisions of each trustee were presented before the second investment in each trustee. Once again they could choose any option (0, 4, 8, 12 MU) and take account of their partners’ past decisions if they wanted to. After the second round of investment, there was a final feedback given displaying the total amount of MU and actual amount of money the participant had earned. The total MU each subject earned consisted of the remaining MU after investment in the first round plus the MU given back by their partners. In fact, the second round only included the investment phase and this was explained to participants afterwards.

Results Questionnaires Independent t-tests on questionnaire scores showed that there were no significant differences between the OXT and PLC group on general trust, trait forgiveness, selfesteem, empathy, depression, anxiety and PANAS scores (see Table 1). There were also no significant differences between the scores of male and female participants (see Table 2). Violation manipulation A repeated-measures analysis of variance (ANOVA) on the benevolence scale scores with violation type (fair vs. violation 1 vs. violation 2 vs. violation 3) as a withinsubject factor and gender (male vs. female) as a betweensubjects factor revealed a significant main effect of violation type (F3,276 = 549.90, p0.24. These results indicated that the violation manipulation was effective in male and female subjects. Trust restoration A repeated-measures ANOVA on investment after receiving repair manipulation with repair strategies (financial compensation vs. apologies vs. fair vs. nothing) as a within-subject factor and drug (OXT vs. PLC), gender (male vs. female) as between-subjects factors only showed a significant main effect of repair strategies (F3,270 = 236.26, p

Oxytocin makes females, but not males, less forgiving following betrayal of trust.

Although oxytocin has been shown to enhance trust behavior, to date no study has directly established whether oxytocin can modulate the effect of repa...
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