Figures and data
Experimental design and task.
(A) Experimental Task. Subjects performed a money-pain trade-off task in which they were designated as deciders. Four conditions (Gain-Self, Gain-Other, Loss-Self, Loss-Other) were introduced across decision contexts (gain vs. loss) and shock-recipients (self vs. other). In each trial, subjects were asked to choose between two options with various amounts of monetary and harm consequences. The chosen option was highlighted for 1s after subjects’ decisions. (B) Procedures of the oxytocin study (study 2). Before the task, a pain calibration procedure was performed on each subject to determine their pain thresholds for electrical shock stimuli. Subjects were then administered with 24IU oxytocin nasal spray or placebo (saline). Thirty-five minutes later, subjects commenced the money-pain trade-off task. Finally, they filled out questionnaires including post-task surveys and assessments of personality traits.
Context specific hyperaltruistic preferences.
(A) In the gain context, subjects chose the less painful option more frequently for others than for themselves, demonstrating a hyperaltruistic preference. However, this tendency was not observed in the loss context. (B) The harm aversion parameter κ for others was significantly greater than that of self in the gain but not the loss context. (C) Furthermore, the relative harm sensitivity, calculated as the difference of regression coefficients of Δs in the other- and self-conditions (otherβΔs − selfβΔs) was significant in the gain context, but not in the loss context. (D) However, the relative money sensitivity, the difference of regression coefficients of Δm in the other- and self-conditions (otherβΔm − selfβΔm), did not show contextual specificity. Error bars represent SE across subjects. NS, not significant; **, P < 0.01; ***, P < 0.001.
Individual difference in moral preferences.
(A-B) Hyperaltruism (κother – κself) was negatively associated with instrumental harm (IH) attitudes but showed no significant relationship with impartial beneficence (IB). (C) The correlation between IH and subjects’ relative harm sensitivities (otherβΔs − selfβΔs) was marginally different between the gain and loss contexts. (D) However, the correlation between IH and subjects’ monetary sensitivities (otherβΔm − selfβΔm) showed no context difference. NS, not significant.
Oxytocin significantly promoted hyperaltruistic preference in the loss context.
(A) In contrast to the placebo condition, oxytocin administration elicited hyperaltruistic behavior (a greater tendency of choosing less painful options between other- and self- recipients) in the loss context compared to the gain context. (B) Model-based hyperaltruistic parameter (κother – κself) showed similar patterns: Hyperaltruistic tendency was reduced by the loss context in the placebo session but restored in the oxytocin session. Error bars represent SE across subjects. NS, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001.
Oxytocin effect on relative harm sensitivities.
(A) Oxytocin significantly modulated the context-specificity of relative harm sensitivity (otherβΔs − selfβΔs). (B) Oxytocin did not influence the contextual differences of the relative monetary sensitivities (otherβΔm − selfβΔm). (C-D) The decision context modulated the correlation between instrumental harm (IH) and subjects’ harm sensitivities in the placebo session (C), whereas oxytocin eliminated the contextual modulation (D). Error bars represent SE across subjects. NS, not significant; *, P < 0.05; **, P < 0.01
Oxytocin modulated the contextual influence on hyperaltruistic behaviors.
(A) Monetary loss (relative to gain) significantly reduced subjects’ perception of harm framing in the task. Oxytocin augmented harm framing perception, particularly in the loss context, effectively removing the contextual specificity of harm framing perception. (B) The conceptual diagram of the moderated mediation model. We assume that the perceived harm framing mediates the relationship between instrumental harm and relative harm sensitivity, with decision context moderating the mediation effect. (C) The moderating effect of decision context was significant under placebo condition. However, oxytocin obliterated the contextual moderation effect by reinstating the mediating role of harm perception in the loss context. Error bars represent SE across subjects. NS, not significant; *, P < 0.05; **, P < 0.01.
Mixed-effect logistic regression analysis results for experiment 1(regression model 1).
Δm and Δs represented the objective differences in money and electric shocks between the more and less painful options. Δs and Δm are numerical variables, while the context (gain vs. loss) and recipient (other vs. self) are categorial variables. The Δs × context × recipient interaction and Δm × context × recipient interaction was further elucidated in Fig. 2C and D. Con: context; Rec: recipient. Error bars represent 95% confidence interval (CI). NS, not significant, * P < 0.05, ** P < 0.01 and *** P < 0.001.
The relationship between personality trait empathic concern (EC) and utilitarian moral personality traits.
Correlation between EC and hyperaltruism (κother – κself), instrumental harm (IH), impartial beneficence (IB) both in the Study1(A-C) and Study 2 (D-E). All the correlations were performed using Pearson correlations.
Association between impartial beneficence (IB) and subjects’ relative harm/monetary sensitivities and monetary sensitivities in Study 1.
IB showed no significant correlation with subjects’ relative harm sensitivities (otherβΔs − selfβΔs) (A), or relative monetary sensitivities (otherβΔm − selfβΔm) (B). The regression coefficients showed the association between IB and relative harm/monetary sensitivities, controlling for empathic concern (EC) and instrumental harm (IH).
Oxytocin and personality traits in study 2.
(A-C) Oxytocin did not affect subjects’ ratings on empathic concern (EC), instrumental harm (IH) or impartial beneficence (IB). Error bars represent SE. NS, not significant.
Relationships between hyperaltruism and utilitarian moral personality traits in Study 2.
(A-B) In the placebo session, hyperaltruistic preferences showed a marginally negative correlation with instrumental harm (IH) but no significant correlation with impartial beneficence (IB). (C-D) In the oxytocin session, hyperaltruistic preferences exhibited significantly negative correlation with IH yet still no significant correlation with IB. The regression coefficients in Figure A, C showed the relationship between IH and moral preference, controlling for empathic concern (EC) and IB, while the coefficient in Figure B, D showed the relationship between IB and moral preference, controlling for EC and IH.
The main results of mixed-effect logistic regression analysis in study 2(regression model 2).
Δm and Δs represented the objective differences in money and electric shocks between the more and less painful options. The Δm × Treat.× Con.× Rec. interaction and Δm × Treat.× Con.× Rec. interaction was further explained in Fig. 5A & B. Treat.: treatment (placebo vs. oxytocin); Con.: decision contexts (gain vs. loss), and Rec.: recipient (self vs. other) are all categorial variables. Error bars represent 95% confidence interval (CI). NS, not significant, * P < 0.05, and *** P < 0.001.
Associations between relative harm/money sensitivities and utilitarian moral personality traits in Study 2.
(A-B) The relative monetary sensitivities were not significantly related with instrumental harm (IH) in either placebo or oxytocin condition. (C-D) In both the placebo and oxytocin conditions, there was no significant correlation between relative harm sensitivity and impartial beneficence (IB). (E-F) No significant correlation was found between relative monetary sensitivities and IB in either the placebo or oxytocin conditions. Figure A & B illustrated the relationship between IH and relative monetary sensitivities, with empathic concern (EC) and IB controlled. Figure C ∼ F described the relationship between IB and relative harm/monetary sensitivities, controlling for EC and IH.
Contribution of EC, IH and IB scores on subjects’ behavior in Study 1.
Contribution of EC, IH and IB scores on subjects’ behavior in Study 2.
