Order versus chaos: The impact of structure on number-space associations

The Spatial-Numerical Association of Response Codes (SNARC) effect has been observed with different stimuli, beside Arabic numerals, such as written/spoken number words, sequences of acoustic stimuli, and groups of elements. Here we investigated how the enumeration of sets of elements can be affected by the spatial configuration of the displayed stimuli with regard to the emergence of the SNARC effect. To this aim, we asked participants to perform a magnitude comparison task with structured (i.e., dice-like) and unstructured (i.e., random) patterns of rectangles. With this manipulation, we sought to explore the presence of the SNARC effect in relation to the structure of the displayed visual stimuli. The results showed that the spatial arrangement of rectangles does not impact visual enumeration processes leading to the SNARC effect. An unexpected reversal of the size effect for unstructured stimuli was also observed. We speculate that the presence of a similar SNARC effect, both with structured and unstructured stimuli, indicates the existence of a common access to the mental number line.