Culture shapes the SNARC-like effect for visual speed.

Numerical and non-numerical quantities are often mapped onto horizontal space. Previous research suggests that culture-related habits, such as reading and writing direction, can influence the orientation of this mapping. While cross-cultural differences have been observed in the spatial representation of time, similar effects have not been consistently found for numbers. This discrepancy has been attributed to the fact that reading and writing involve the sequential processing of information in a specific direction but are not inherently related to numerical content. These findings support the hypothesis that the spatial representation of magnitudes depends on specific experiential associations. The present study investigated potential cross-cultural differences in the spatial representation of visual speed by comparing participants from Italy, who use a left-to-right reading and writing system, with participants from Iran, who use a right-to-left system. Participants judged whether the speed of a centrally presented random dot kinematogram was slower or faster than a reference, using left or right response keys. Results revealed opposite spatial mappings of visual speed: a left-to-right mapping for Italian participants and a right-to-left mapping for Iranian participants. These findings support the view that reading and writing direction shapes the spatial representation of magnitudes intrinsically linked to directional reading experiences, such as motion at a specific speed.