# Motion-numerical compatibility affects magnitude classification

## TL;DR

This study shows that moving the head horizontally helps people process numbers more efficiently when the movement direction matches the number's size.

## Contribution

The study demonstrates a horizontal motion-numerical compatibility effect using head movements, extending beyond traditional button-press methods.

## Key findings

- Participants responded faster to number classification under MNL-congruent conditions on both horizontal and vertical axes.
- A congruency effect between number magnitude and head direction was observed, but only on the horizontal axis.
- Horizontal head movements appear to shift spatial attention, aiding in magnitude processing.

## Abstract

Number concepts are spatially organized along a mental-number line (MNL) with smaller magnitudes represented in left/lower space and larger magnitudes progressively toward right/upper space. Evidence for this association largely relies on simple button responses. We investigated the generality of this association with directional head movements. In a preliminary test, 31 neurotypical adults classified spoken numbers with lateralized buttons faster under MNL-congruent than incongruent conditions along both horizontal and vertical axes. Having established the standard number-space association, participants then performed a Go/No-go version of our task with concurrent horizontal or vertical head movements. The results showed a congruency effect between number magnitude and head direction—which was limited to the horizontal axis. Our results suggest that horizontal motion induces spatial attention shifts which facilitate spatially congruent magnitude processing, thus supporting a conceptual association of space and magnitude.