BACKGROUND Human parental care relies heavily on the ability to monitor and respond to a child's affective states. The current study examined pupil diameter as a potential physiological index of mothers' affective response to infant facial expressions. METHODS Pupillary time-series were measured from 86 mothers of young infants in response to an array of photographic infant faces falling into four emotive categories based on valence (positive vs. negative) and arousal (mild vs. strong). RESULTS Pupil dilation was highly sensitive to the valence of facial expressions, being larger for negative vs. positive facial expressions. A separate control experiment with luminance-matched non-face stimuli indicated that the valence effect was specific to facial expressions and cannot be explained by luminance confounds. Pupil response was not sensitive to the arousal level of facial expressions. CONCLUSIONS The results show the feasibility of using pupil diameter as a marker of mothers' affective responses to ecologically valid infant stimuli and point to a particularly prompt maternal response to infant distress cues.

中文翻译：

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母亲对婴儿面部表情的瞳孔反应。

背景技术人类的父母照料在很大程度上依赖于监视和应对儿童的情感状态的能力。目前的研究将瞳孔直径作为母亲对婴儿面部表情的情感反应的潜在生理指标。方法对86名年幼母亲的瞳孔时间序列进行了测量，以根据价数（正与负）和唤醒（轻度与强壮）将一系列照相婴儿面部分为四个情感类别。结果瞳孔扩张对面部表情的价态高度敏感，阴性面部表情和阳性面部表情的放大幅度更大。单独的具有亮度匹配的非面部刺激的对照实验表明，化合价效应是面部表情所特有的，无法用亮度混淆来解释。学生的反应对面部表情的唤醒水平不敏感。结论结果表明，使用瞳孔直径作为母亲对生态上有效的婴儿刺激的情感反应的标志是可行的，并指出母亲对婴儿窘迫线索的反应特别迅速。