Numbers and space are strongly related in the human mind. In particular, small and large numbers are mentally linked to spatial directions, forming the so‐called mental number line. Traditionally, the direction of the number line was thought to emerge from cultural spatial experience with reading and writing. In this article, we review recent developmental data that put constraints on this traditional account and suggest that directional number representation develops even before the acquisition of literacy. On the basis of these data, we argue that the link between numbers and space is triggered by systematic involvement in directional actions of any kind rather than by reading and writing per se. Before school begins, children are exposed to many directional cues by observing the world around them and interacting with their parents. We propose a hypothetical mechanism through which this preliterate experience might activate spatially oriented numerical representation.