Abstract

Sensitivity to others’ actions is essential for social animals like humans and a fundamental requirement for any kind of social cognition. Unsurprisingly, it is present in humans from early in the first year of life. But what processes underpin infants’ sensitivity to others’ actions? Any attempt to answer this question must solve twin puzzles about the development of goal tracking. Why does some, but not all, of infants’ goal tracking appear to be limited by their abilities to represent the observed action motorically at the time it occurs? And why does their sensitivity to action sometimes manifest itself differently in dishabituation, pupil dilation and anticipatory looking? Solving these twin puzzles is critical for understanding humans’ earliest sensitivity to others’ actions. After introducing the puzzles, this paper argues that solving them may require identifying multiple, distinct processes for tracking the targets and goals of actions.