Spatial components of numerical and ordinal information: origins and development

We have found that by the age of 7-8 months, infants exhibit preferences for numerical ordinal series that are spatially presented from left to right, but only when they follow an increasing order, mirroring adults’ left-to-right oriented ‘mental number line’. These findings suggest that the spatial directionality that numerical information takes does not depend on cultural or symbolic devices, as it is present in preverbal infants. As a consequence of this spatial-numerical mapping, we have shown that infants’ attentional orienting is influenced by numerical magnitude, with a small non-symbolic number accelerating detection of a left-sided target, and a large non-symbolic number accelerating detection of a right-sided target. Moreover, we have shown that the left-to-right presentation boosts serial learning in infants.