Do infants think that agents choose what’s best?

The naïve utility calculus theory of early social cognition argues that by relating an agent’s incurred effort to the expected value of a goal state, young children and infants can reason about observed behaviors. Here we report a series of experiments that tested the scope of such utility-based reasoning adopted to choice situations in the first year of life. We found that 10-month-olds (1) did not expect an agent to prefer a higher quantity of goal objects, given equal action cost (Experiment 1) and (2) did not expect an agent to prefer a goal item that can be reached at lower cost, given equal rewards (Experiment 2a and 2b). Our results thus suggest that young infants’ utility calculus for action understanding may be more limited than previously thought in situations where an agent faces a choice between outcome options.