Joint Attention without Gaze Following: Human Infants and Their Parents Coordinate Visual Attention to Objects through Eye-Hand Coordination

The coordination of visual attention among social partners is central to many components of human behavior and human development. Previous research has focused on one pathway to the coordination of looking behavior by social partners, gaze following. The extant evidence shows that even very young infants follow the direction of another's gaze but they do so only in highly constrained spatial contexts because gaze direction is not a spatially precise cue as to the visual target and not easily used in spatially complex social interactions. Our findings, derived from the moment-to-moment tracking of eye gaze of one-year-olds and their parents as they actively played with toys, provide evidence for an alternative pathway, through the coordination of hands and eyes in goal-directed action. In goal-directed actions, the hands and eyes of the actor are tightly coordinated both temporally and spatially, and thus, in contexts including manual engagement with objects, hand movements and eye movements provide redundant information about where the eyes are looking. Our findings show that one-year-olds rarely look to the parent's face and eyes in these contexts but rather infants and parents coordinate looking behavior without gaze following by attending to objects held by the self or the social partner. This pathway, through eye-hand coupling, leads to coordinated joint switches in visual attention and to an overall high rate of looking at the same object at the same time, and may be the dominant pathway through which physically active toddlers align their looking behavior with a social partner.社交伙伴间的视觉注意协调，是人类行为表现与个体发展进程中诸多核心环节的关键基础。过往相关研究多聚焦于社交伙伴间注视行为协调的一条路径——视线追随（gaze following）。现有研究证据表明，即便极低龄婴儿也会追随他人的视线方向，但此类行为仅能在高度受限的空间情境中发生：这是由于视线方向并非指向视觉目标的精准空间线索，且难以在空间复杂度较高的社交互动中加以运用。本研究通过对1岁婴儿与其父母主动玩玩具时的眼动视线进行逐时刻追踪，为目标导向行为中的手眼协调这一替代性路径提供了新的实证依据。在目标导向行为中，行为者的手部与眼部动作在时间与空间维度上均紧密耦合；因此，在涉及物体手动操作的情境中，手部动作与眼动可为观察者提供关于视线落点的冗余信息。本研究结果显示，在上述情境中，1岁婴儿极少注视父母的面部与眼部；相反，婴儿与父母无需借助视线追随，仅通过关注自身或社交伙伴所持有的物体，即可实现注视行为的协调。这一基于手眼耦合（eye-hand coupling）的路径，可促成视觉注意的协同同步切换，整体上提升了双方同时注视同一物体的概率，且可能是身体活动活跃的学步儿与社交伙伴实现注视行为对齐的主导性路径。