Through Another's Eyes: Implicit SNARC-like Attention Bias Reveals Allocentric Mapping of Numerical Magnitude

Numerical magnitude can bias spatial attention, typically facilitating faster responses to the left for small numbers and to the right for large numbers-an effect traditionally attributed to egocentric spatial mappings. However, in everyday environments, individuals often share space with others, raising the question of whether such spatial-numerical associations can spontaneously reorganize based on another person's visual perspective. To investigate this, we employed a digit-primed visual detection paradigm in which participants judged the location (left, right, up, or down) of a briefly presented peripheral probe following centrally displayed digits. If numerical magnitude implicitly guides attention, probe detection should be faster when its location is congruent with the digit-induced spatial bias. Critically, in the avatar condition, a task-irrelevant avatar was positioned on the participant's left side, such that the avatar's horizontal (left-right) axis corresponded to the participant's vertical (up-down) axis-an axis along which egocentric numerical biases are typically absent. If participants spontaneously adopted the avatar's perspective, numerical cues might induce attentional biases along this axis. Results revealed two simultaneous effects: a canonical egocentric SNARC-like effect (small-left, large-right) and a novel allocentric effect (small-up, large-down) emerged along the vertical axis, implicitly aligned with the avatar's left-right spatial orientation. Numerical extremity enhanced the egocentric SNARC-like effect but had no effect in the allocentric case, pointing to a distinct mechanism rooted in embodied spatial perspective. These findings suggest that numerical magnitude can implicitly map onto both egocentric and allocentric spatial frames, reflecting a implicit and embodied mechanism of social understanding.