Abstract: Recent studies have shown that human visual perception and attentional selection near the hands are substantially altered compared with stimuli far from the hands. For example, visual stimuli near the hands are detected more quickly, discriminated more accurately and processed more thoroughly compared far from the hands. This cluster effect of hand-stimulus proximity on vision is termed "hand proximity effect". Recent studies have shown that human visual perception and attentional selection near the hands are substantially altered compared with stimuli far from the hands. For example, visual stimuli near the hands are detected more quickly, discriminated more accurately and processed more thoroughly compared far from the hands. This cluster effect of hand-stimulus proximity on vision is termed "hand proximity effect (HPE)". The research on the HPE have flourished in the past ten years. The purpose of this essay, therefore, is to provide a systematically review of the existing body of literature. Research repeatedly found that placing hands near stimuli enhances perceptual processing and spacial working memory while impairs perceptual group and object-based perception. However, the results of hand-stimulus proximity's effect on executive control were inconsistent. Moreover, placing hands near the stimuli facilitates processing information relevant to grasp affordances. Thus, the affordance for specific actions moderates the HPE. The ownership of hand is another moderator. It is suggested that participants' own hand but not other's hand or fake hand near to the stimuli can affect visual processing. If the fake hand is somatically and visually similar to real hand, however, putting fake hand near the stimuli can affect visual processing. After cooperated to accomplish a task, other’s hand near the stimuli can induce HPE too. Consistent with embodied cognition theory, the attention theories proposed action-based explanations of HPE: objects near the hands candidate for action, thus they receive enhanced processing. There are two attention theories for HPE. The attentional priority theory suggests that hand-stimulus proximity affects early visual processing, whereas the delayed disengagement theory suggests that hand-stimulus proximity affects later visual processing. However, a recent study used event-related potentials found that the effect of hand-stimulus proximity on the visual processing ranges from early sensory processing to later cognitive processing. Two distinct theoretical accounts explain neural mechanism of HPE. The bimodal visuo-tactile neurons account suggests that stimuli in peri-hand space may activate the bimodal visuo-tactile neurons. Thus, the visual targets near the hand may be more salience than targets far from the hand because there are additional neural substrates representing the objects in peri-hand space. However, the trade-off of two visual pathways account suggests objects near the hand induce a bias toward the action-oriented magnocellular visual pathway. Conversely, objects far from the hand bias vision toward the perception-oriented parvocellular visual pathway. Future research should focus on the neural mechanisms, and the practical applications of the HPE. Moreover, the modulation of action-affordance, and the modulation of interpersonal and social factors on HPE may be promising in the future studies.

Key words: hand proximity effect, attention, embodied cognition, bimodal visual-tactile neuron, two visual pathways

摘要： 把手放在刺激旁边，会对知觉、记忆、语义和执行控制等认知加工产生影响，这类现象被称为手近效应。手近效应反映了身体与环境的互动对认知的塑造作用，为具身认知提供了新证据。本文从手近效应的内容，影响因素，及其认知、神经机制等方面对相关研究进行梳理。并从手近效应的神经机制，应用研究，以及动作意图和人际社会因素的调节作用等方面探讨当前手近效应还未解决的问题。

关键词: 手近效应 注意 具身认知 视触双通道神经元 视觉通路