Serotonin transporter genotype influences eye position and pupil diameter when observing social images.
(A) In contrast to L/L monkeys, S/L monkeys looked less at the picture when the image depicted a face than when it depicted a scrambled face (* indicates p = 0.02) and (B) spent less time looking in the eye region when face images were presented. Additionally, both L/L and S/L monkeys spent less time looking in the eye region of high status faces than low status faces (* indicates p = 0.02, ** indicates p = 0.01). (C) When observing faces, the pupil diameter of S/L monkeys was modulated by the social status of the displayed face, with a greater mean pupil diameter induced by the presentation of high-status faces (* indicates p = 0.05). In contrast, no significant difference in the pupil diameters of L/L animals was observed to correlate with image category.