Spatial and numerical processing in children with non-verbal learning disabilities

• A strong association between numbers and space has been repeatedly demonstrated.
• We investigated whether non-verbal learning disability (NVLD) affects numerical reasoning.
• Spatial and numerical performances of NVLD and control children were compared.
• NVLD changes the nature of the mental number line.
• NVLD also leads to a decrease of the mental number line's accuracy.

Consistently with the idea that numbers and space interact with each other, the present paper aimed to investigate the impact of non-verbal learning disabilities (NVLD) on spatial and numerical processing. In order to do so, 15 NVLD and 15 control children were required to perform different spatial (the line bisection and Simon tasks) and numerical tasks (the number bisection, number-to-position and numerical comparison tasks). In every task, NVLD children presented lower accuracy scores than the control group. While both groups manifested similar pseudo-neglect and Simon effects, they however differed in the numerical comparison task: while control children presented the standard SNARC effect in the uncrossed and crossed postures, no SNARC effect was observed in the NVLD group. Our results therefore suggest that NVLD affects the accuracy and the nature of the mental number line by decreasing its precision and the saliency of its left-to-right orientation.