Knowing before doing: Review and mega-analysis of action understanding in prereaching infants

The relationship between experience and knowledge is one of the oldest and deepest questions in psychology. In developmental science, research on this question has focused on prereaching infants who cannot yet retrieve objects by reaching for and grasping them. Over the past 2 decades, behavioral research in this population has produced two seemingly contradictory findings: After first-person experience with reaching via "sticky mittens" training, (a) infants come to expect that people reach efficiently, toward goal objects, but (b) under some conditions, they can express these expectations without training. We hypothesize that prereaching infants' understanding of other people's actions is driven by the representational demands of the tasks used to test their abilities, rather than by first-person motor experience per se. We conducted a qualitative review and a quantitative, preregistered "mega-analysis" of the original data from this past work (i.e., an analysis of looking responses from N = 650 infants, 30 conditions, and 8 articles). We found that the manipulations with the strongest effects (measured via effect sizes and Bayes factors) on infants' understanding of other people's goals and physical constraints, controlling for infant age, were abstract features of action: Whether the action produced an observable effect in the world on contact and provided unambiguous evidence for the actor's goal. We end by presenting a broad hypothesis about how young infants learn about other people's minds and actions, centered on an early intuitive theory of action planning, to be tested with future work. (PsycInfo Database Record (c) 2023 APA, all rights reserved).