The Number Sense and its link with child math abilities
CVRS2019, Child Vision Society Research Society Meeting 2019
15-17/06/2019 Fondazione Stella Maris a Pisa
Introduction: Almost from birth, humans possess what may be called a “number-sense”, the capacity to estimate numerosity. Many studies have shown that numerosity estimation correlates strongly with math abilities, with discalculic (DD) children showing particularly high thresholds. We recently demonstrated the existence of three numerosity sub-systems, for low, medium and high numerosities. Here we ask whether: 1) the three numerosity subsystems all predict math performance; 2) the DD deficit is specific for numerosity; 3) the functional architecture of the numbersense is organized differently in DDs than typicals. Methods: We correlated math abilities with psychophysically measured numerosity thresholds for a broad range of numerosities. With dyscalculic participants, we measured discrimination thresholds, perceptual adaptation and serial dependence (two indices of functional architecture), both for numerosity and non-numerical indexes (size). Results: The results showed that during typical development, math abilities are linked to numerosity thresholds measured for intermediate (estimation), not very small (subitizing) nor very large (texture) numerosities. We also found that numerosity but not size thresholds were impaired in dyscalculia. Finally, perceptual adaptation and serial dependence were unimpaired in dyscalculia. Conclusions: The results suggest that: 1) while the “number-sense” is sub-served by many perceptual sub-systems, the link with math is specific for intermediate numerosities (estimation-range); 2) while numerosity thresholds are selectively higher in dyscalculia, the mechanisms for perceiving numerosity are otherwise similar, suggesting that that have a similar, but perhaps noisier, number sense.