The link between number-space associations and visuospatial abilities depends on visualization profile

Background:
Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster RTs to small/large digits with the left/right hand respectively. However, the cognitive origin of the effect remains elusive. Previous studies suggested that it might depend on visuospatial processes, since individuals with better performances in 2D (but not 3D) mental rotation tasks displayed weaker number-space associations (Viarouge et al., 2014).
Aims:
Given the high inter-individual variability of number-space associations, we determined whether the SNARC effect always relies on visuospatial processes or whether its cognitive origin varies with visualization preferences.
Method:
We distinguished between object-visualizers (n=42, 23 female, age=22.93) and spatial-visualizers (n=42, 15 female, age=23.9) using the Object-Spatial Imagery Questionnaire (Blajenkova et al., 2006). All participants performed the parity judgment task, a 2D visuospatial test and a 3D mental rotation task.
Results:
In object-visualizers, weaker SNARC slopes were associated with better performances in the 2D (r=0.46, p=0.004), but not 3D (r=-0.04, p=0.79) task, thereby replicating previous observations. Conversely, in spatial-visualizers, the performances in both visuospatial tasks were unrelated to the SNARC effect (2D: r=0.02, p=0.89; 3D: r=0.2, p=0.22).
Conclusions:
These findings suggest that in object-visualizers, number-space associations and 2D performances underlie common visuospatial processes. Conversely, in spatial-visualizers, number-space associations seem to result from cognitive mechanisms other than those recruited during the aforementioned visuospatial tasks (e.g., verbal-spatial coding mechanisms).
All in all, we were able to further unravel the mechanisms underlying number-space associations and could highlight visualization preferences as an additional explanation for the great inter-individual variability of the SNARC effect.