Data from: Automatic facial mimicry in response to dynamic emotional stimuli in five-month-old infants

Human adults automatically mimic others' emotional expressions, which is believed to contribute to sharing emotions with others. Although this behaviour appears fundamental to social reciprocity, little is known about its developmental process. Therefore, we examined whether infants show automatic facial mimicry in response to others' emotional expressions. Facial electromyographic activity over the corrugator supercilii (brow) and zygomaticus major (cheek) of four- to five-month-old infants was measured while they viewed dynamic clips presenting audiovisual, visual and auditory emotions. The audiovisual bimodal emotion stimuli were a display of a laughing/crying facial expression with an emotionally congruent vocalization, whereas the visual/auditory unimodal emotion stimuli displayed those emotional faces/vocalizations paired with a neutral vocalization/face, respectively. Increased activation of the corrugator supercilii muscle in response to audiovisual cries and the zygomaticus major in response to audiovisual laughter were observed between 500 and 1000 ms after stimulus onset, which clearly suggests rapid facial mimicry. By contrast, both visual and auditory unimodal emotion stimuli did not activate the infants' corresponding muscles. These results revealed that automatic facial mimicry is present as early as five months of age, when multimodal emotional information is present.成年人类会自动模仿他人的情绪表情，该现象被认为是个体间情绪共享的重要基础。尽管此类行为被视作社会互惠的核心特征之一，但学界对其发展历程仍知之甚少。为此，本研究旨在探究婴儿是否会对他人的情绪表情产生自动面部模仿行为。本研究记录了4至5月龄婴儿皱眉肌（corrugator supercilii）与颧大肌（zygomaticus major）的面部肌电活动，实验过程中向婴儿呈现包含视听、视觉及听觉三类情绪刺激的动态片段。其中，视听双模态情绪刺激为伴随情绪匹配发声的大笑/哭泣面部表情；而视觉单模态与听觉单模态情绪刺激则分别为搭配中性发声的情绪面部表情，以及搭配中性面部表情的情绪发声。在刺激起始后500至1000毫秒的时间窗口内，婴儿的皱眉肌在响应视听哭泣刺激时激活水平显著提升，颧大肌在响应视听大笑刺激时同样出现激活增强，该结果明确提示婴儿具备快速面部模仿能力。与之相对，视觉单模态与听觉单模态情绪刺激均未引发婴儿对应肌肉的激活。本研究结果表明，当接收到多模态情绪信息时，自动面部模仿行为早在婴儿5月龄时便已出现。