Plasticity of Peripersonal Space and Comfortable Distance Around the Feet in Response to Threats

PPS (peripersonal space) is broadly defined as the area in which humans interact with and defend against nearby stimuli in a multisensory world. This space is not rigidly fixed but exhibits plasticity that adapts to the nature of the presented stimuli. Another related concept is comfortable distance, the minimal distance at which individuals feel at ease, which participants typically determine subjectively. While PPS and comfortable distance share similarities in their defensive functions, little is known about the differences and overlap in their underlying mechanisms. To date, most research has predominantly focused on the upper limbs, particularly the hands, leaving the flexibility of PPS around the lower limbs largely unexplored. Our study aims to address this gap by presenting stimuli near participants' feet. The experiment consists of two components: one group of participants will perform a visuotactile task, while another will determine the minimal comfortable distance. This study seeks to answer two key questions: （1）Does the PPS around the feet vary with the valence of stimuli? （2）What are the similarities and differences in the spatial mechanisms underlying PPS and comfortable distance?