Born with an abstract code for number: evidence from cross-modal and cross-format neural adaptation in the first three days of life

One of the most astonishing abilities documented in human newborns is their capacity to spontaneously match sets of items on the basis of their number, even when they are presented in different modalities (auditory and visual) and formats (sequential and simultaneous). These behavioural findings suggest that the newborn brain comes to life endowed with a system that encodes number in an abstract, supramodal format, but direct neural evidence for such a representation is lacking. Using high-density EEG and a frequency-tagging paradigm, we measured neural entrainment to periodically presented visual arrays that were either numerically congruent or incongruent with previously familiarized and concurrently presented auditory sequences in 21 newborns (0-3 days old). The amplitude of neural entrainment to the visual arrays provided a robust index of cross-modal numerical congruency: it was significantly reduced for numerically congruent relative to incongruent stimuli. This cross-modal and cross-format numerosity-specific repetition suppression effect provides evidence for an abstract code for number in the newborn brain, reinforcing the view that number constitutes a foundational dimension of human perception since birth.