Number-action mapping in human newborns

Humans' ability to link sensory signals across different modalities and dimensions is functional from birth. Moreover, they form expectations of congruent magnitude changes across dimensions such as number, spatial extent, and temporal duration, anticipating that increases (or decreases) in one dimension will be matched by similar changes in another. Here, we investigated whether newborns can also map numerical magnitude onto action-related information—specifically, hand aperture amplitude—a form of mapping previously observed in adults, children, and infants, but not yet studied at birth. Across three experiments (16 newborns per experiment; N = 48), we presented newborns with changes in both number and hand aperture. Newborns preferred (i.e., looked longer at) congruent pairings only when the stimuli involved biological hands (Experiment 1), but not when congruency was disrupted (Experiment 2) or replaced with non-biological aperture configurations (Experiment 3). These results rule out a general novelty explanation, support the presence of an abstract magnitude mapping, and indicate that this mapping is not driven by abstract aperture configurations based solely on the distance or proximity between objects. The findings provide initial evidence that action–number mappings may already be present at birth, suggesting that the connection between sensorimotor processes and numerical cognition could be available from the earliest stages of postnatal life.