Buiatti, M.; Eccher, E.; Petrizzo, I.; Pradal, U.; Taddei, F.; Vallortigara, G.; Izard, V.; Piazza, M.

Whether humans possess an abstract sense of number at birth, and how it is implemented in the brain, remain open questions. Here, using high-density EEG and a frequency-tagging paradigm, we investigated these questions by measuring neural responses in 21 newborns (0-3 days old) to visual arrays that were either numerically congruent or incongruent with previously familiarized auditory sequences. Despite newborns' limited attentional span, robust visual steady-state responses were observed across all conditions. Critically, response amplitude was significantly reduced for numerically congruent relative to incongruent stimuli. This early form of cross-modal numerosity repetition-suppression mechanism provides direct neural evidence that newborns encode numerosity across modalities in an abstract, supramodal format within the first days of life. These results support the view that number constitutes a foundational dimension of human perception and that sensitivity to this parameter is part of the innate toolkit present at birth.