Ten-month-olds infer relative costs of different goal-directed actions

While it is straightforward to compare the costs of different variants of the same action (e.g., walking to a coffeeshop at the end of the block will always be less costly than walking to a coffeeshop three blocks away), the relative costs of different actions are not directly comparable (e.g., would it be easier to jump over or walk around a fence?). Across two experiments we demonstrate that 10-month-old infants spontaneously encode the manner of different goal-directed actions (jumping over an obstacle vs. detouring around it, Experiment 1) and use the principle of cost-efficiency to infer their relative costs (jumping is less costly to bypass low walls, but detouring is less costly to bypass high walls, Experiment 2). By relating action choices to the physical parameters of the environment, infants identify the least costly actions given the circumstances, which allows them to make behavioral predictions in new environments and may also enable them to infer others' motor competence.