Plasma OT levels
The average oxytocin level is 214± SD 230 pg/ml (Figure S1C) which is representative of the assay procedure used in the current investigation [8]. We test whether age and gender might have an effect on plasma OT level. As usually observed [36], [37], in linear regression, there is no significant gender difference in plasma OT levels (p>0.365) (Figure S2C), and also no significant age effect on Plasma OT (p>0.650). Following other investigations [38], [39], we exclude 23 subjects whose plasma OT exceed 3 standard deviations (>904) from the subsequent analysis (Figure S1C), and then use the log transformation in the analysis.