Data from: Pupil dilation as an index of preferred mutual gaze duration

Most animals look at each other to signal threat or interest. In humans,
this social interaction is usually punctuated with brief periods of mutual
eye contact. Deviations from this pattern of gazing behaviour generally
make us feel uncomfortable and are a defining characteristic of clinical
conditions such as autism or schizophrenia, yet it is unclear what
constitutes normal eye contact. Here, we measured, across a wide range of
ages, cultures and personality types, the period of direct gaze that feels
comfortable and examined whether autonomic factors linked to arousal were
indicative of people's preferred amount of eye contact. Surprisingly,
we find that preferred period of gaze duration is not dependent on
fundamental characteristics such as gender, personality traits or
attractiveness. However, we do find that subtle pupillary changes,
indicative of physiological arousal, correlate with the amount of eye
contact people find comfortable. Specifically, people preferring longer
durations of eye contact display faster increases in pupil size when
viewing another person than those preferring shorter durations. These
results reveal that a person's preferred duration of eye contact is
signalled by physiological indices (pupil dilation) beyond volitional
control that may play a modulatory role in gaze behaviour.