Fig. 4.

Oxytocin pre-treatment caused significantly larger stimulus-induced pupil dilation (A). Pupil responses in the oxytocin session were significantly larger than in the placebo session during the 1000–3000 ms interval after stimulus onset. Task-induced pupil dilation correlated with individual variability in emotional sensitivity towards differences in subtle expressions (r = –0.376, P < 0.01). Those with the lowest sensitivity showed larger pupil dilation during stimulus presentation, consistent with higher task difficulty for these participants. As illustrated by the median split analysis (C), oxytocin’s beneficial effects on emotional sensitivity in the low sensitivity group were not underpinned by large increases in pupil dilation. In contrast, we found a trend towards a group-by-treatment interaction driven by a larger oxytocin-induced increase in pupil dilation in the high emotional sensitivity group.