A rich concept of magnitude-in its numerical, spatial, and temporal forms-is a central foundation of mathematics, science, and technology, but the origins and developmental relations among the abstract concepts of number, space, and time are debated. Are the representations of these dimensions and their links tuned by extensive experience, or are they readily available from birth? Here, we show that, at the beginning of postnatal life, 0-to 3-dold neonates reacted to a simultaneous increase (or decrease) in spatial extent and in duration or numerical quantity, but they did not react when the magnitudes varied in opposite directions. The findings provide evidence that representations of space, time, and number are systematically interrelated at the start of postnatal life, before acquisition of language and cultural metaphors, and before extensive experience with the natural correlations between these dimensions.T he origins of the abstract concepts of space, time, and number are longstanding topics of study, from the dawn of philosophy (1) and experimental psychology (2) to classical developmental psychology (3) and modern cognitive science (4-6). Kant (7) argued that representations of number, space, and time provide "a priori" intuitions and concepts that precede and structure all experience. Modern cognitive science provides methods to test these ideas experimentally. We now know that human newborns, and even inexperienced animals such as newly hatched chicks, are able to discriminate objects on the basis of numerosity a few hours after the start of postnatal experience (8, 9). When human newborns are presented with auditory sequences of syllables and visual arrays of objects, they look longer at the arrays that correspond to the auditory sequences in number than at arrays differing in number by a 1:3 ratio (8, 10). At birth, humans thus possess representations of approximate numerosity that are abstract enough to enable a generalization across stimuli as varied as sequences of syllables and sets of visual objects. Are newborn human infants able to perform further, yet more abstract, generalizations across different types of magnitudes?Humans draw links between the dimensions of space, time and number, as shown by the presence of "number lines" (11, 12) and the use of spatial language to refer to time (13). Human adults link these dimensions automatically. When processing spatial and temporal, or spatial and numerical information simultaneously, representations of time and number are both affected by the spatial dimension (14, 15). The propensity to represent numerical magnitudes by the lengths of line segments (number lines) is a widespread phenomenon not only across cultures and species but also over human development. Human infants (16, 17), children (18, 19), educated human adults (18,20), and uneducated adults living in remote cultures (11) map numbers onto corresponding line lengths. Similarly, spatial-temporal mappings show the universal effects of one of these dimensions on the other, both in human a...