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.多数动物通过相互注视来传递威胁或兴趣信号。在人类的社会互动中，这类互动通常会穿插短暂的双向目光接触。偏离此类注视行为模式的情况通常会令个体产生不适感，同时也是自闭症（autism）、精神分裂症（schizophrenia）等临床病症的标志性特征之一，但目前学界尚未明确何为正常的目光接触。本研究覆盖了广泛的年龄、文化与人格类型群体，测量了个体感到舒适的直接注视时长，并探究了与生理唤醒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，研究发现个体偏好的注视时长并不依赖于性别、人格特质或吸引力等基础特征。但本研究确实发现，反映生理唤醒的细微瞳孔变化，与个体感到舒适的目光接触时长存在显著关联。具体而言，偏好更长时长目光接触的个体，在观察他人时的瞳孔尺寸增速快于偏好较短时长目光接触的个体。上述结果表明，个体偏好的目光接触时长可通过不受意志控制的生理指标（瞳孔扩张）来体现，此类指标或对注视行为起到调节作用。