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.多数动物会通过对视传递威胁或意图信号。对人类而言，这类社交互动通常会穿插短暂的双向目光接触。偏离这一凝视行为模式的情况往往会令我们感到不适，同时也是自闭症（autism）、精神分裂症（schizophrenia）等临床病症的典型特征之一，但目前学界尚未明确何为正常的目光接触。本研究针对不同年龄、文化背景与人格类型的多样人群，测量了令受试者感到舒适的直接对视时长，并探究了与唤醒状态相关的自主神经因素是否可用于反映个体偏好的目光接触量。令人意外的是，我们发现个体偏好的凝视时长并不受性别、人格特质或外貌吸引力等基础特征的影响；不过我们确实观察到，反映生理唤醒状态的细微瞳孔变化，与个体感到舒适的目光接触量存在显著相关。具体而言，相较于偏好较短对视时长的人群，偏好较长对视时长的个体在观察他人时，瞳孔尺寸会出现更快的增大。上述研究结果表明，个体偏好的对视时长可通过不受意志控制的生理指标（瞳孔扩张（pupil dilation））来体现，这类指标或许会对凝视行为起到调节作用。