The influence of self-experienced Iconic finger-postures on Numerical processing: Hemispheric asymmetries in semantic integration.

Main theories of embodied cognition assume that arbitrary abstract concepts (e.g., words, numbers) are understood through their grounding in our sensory-motor system. Recent evidence shows that performing iconic finger embodied gestures (finger-montring) primes number processing, suggesting a shared numerical semantic representation between Arabic and finger-numeral representations. However, it is still unknown in which hemisphere this cross-talk could happen. To investigate where the cross-modal semantic priming between self-experienced iconic finger-postures and visual Arabic digit processing would occur in the brain, we tested educated adults in a simple numerical identification task with lateralized stimuli, while they covertly executed task-irrelevant finger-montring configurations. Participants were instructed to identify a set of Arabic digits (2-3-4) presented in each hemisphere by Divided Visual Field (DVF) paradigm responding with one hand, while the non-responding hand was fixed in canonical (iconic) or non-canonical (non-iconic) finger-posture. Results showed that RTs for Arabic digit (e.g., 3) identification were faster in left hemisphere, particularly when participants’ non-responding hand was fixed in canonical configuration compared to non-canonical configuration, but only when both bodily-hand information and visual stimuli were matched simultaneously within the left hemisphere. On the other hand, no semantic priming was found when both stimuli (body and visual) were matched in the right hemisphere. These results suggest that own proprioceptive perception of finger-numeral postures primes symbolic number processing in left hemisphere but not in the right, at least for small numbers. Taken together, we illustrate a clear hemispheric asymmetry in the semantic integration between iconic finger-numeral and Arabic-digit representations.