Do infants’ social evaluations privilege the outcomes of others’ actions, or the beliefs underlying those actions? In two experiments, 8-month-old infants viewed a protagonist who sought to grasp one of two toys, each inside a different box, as two other agents observed. Then, while the protagonist was away, the toys exchanged locations, either in the presence or absence of the two other agents. Thus, the agents had either true or false beliefs about the toys’ locations. When the protagonist returned, one agent opened the box that now contained the protagonist’s desired toy, whereas the other opened the box that previously contained that toy. When agents had true beliefs about the desired toy’s location, infants preferred the agent who opened the box containing that toy. When agents had false beliefs about that location, infants instead preferred the agent who opened the opposite box. Thus, infants' social evaluations privilege agents’ beliefs.

Research provides evidence that infants infer what others can and cannot see from their differing perspectives, but do infants appreciate that their own perspective on an object can differ from that of a person who views the same object from a different direction? First, infants were shown two faces with screens in front of or behind them. Infants correctly inferred that a face that was visible to them was occluded to a person sitting across from them. Then two experiments presented infants with two unscreened faces: one upright and one inverted. Infants attributed their own perspective on those faces to the other person: They did not appreciate that faces that were upright to them were inverted to the other person. Thus, infants appreciate that others may see things that they do not, but they fail to grasp not that others may experience the same visible objects differently than they do.

When people act on objects, their goals can depend on the objects’ intrinsic properties and conventional uses (e.g., using forks, not knives, to eat spaghetti), locations (e.g., clearing the table, regardless of what is on it), or both (eating with the fork next to your plate, not your dining partner’s). For adults, objects’ intrinsic properties matter more than their locations in most action contexts. Whereas 5-month-old infants privilege objects’ intrinsic properties in attributing goals to people reaching for objects, 3-month-old infants do not. Do younger infants fail to view reaching as goal-directed, or are they uncertain which properties of objects are relevant in different contexts? Here we show that 3-month-old infants attribute goals to others’ reaching actions when given information that their actions depend on what, not where, an object is. Our findings suggest that 3-month-old infants can learn about others’ object goals, before they reach for objects themselves.

Not every prosocial act is equally praiseworthy. As adults, we tend to evaluate helpers depending on others’ needs; helping someone with a hard task may be more burdensome but also more prosocial than helping someone with an easy task. Despite growing evidence that infants are sensitive to the costs of others’ actions, whether such representations inform their evaluation of prosocial acts remains an open question. Here, we ask whether 16-month-olds’ preference between two helpers is sensitive to task difficulty. Infants preferentially reached for (Exp. 1), and looked at (Exp. 2), an agent who helped someone facing a high-cost task over an agent who helped someone facing a low-cost task. Such preference disappeared when the agents completed the same tasks in a self-serving context. These results suggest that infants use action cost not only to predict and explain others’ behaviors but also to evaluate others in prosocial contexts.

Do children reason that people in close relationships accurately represent each other's minds? In two experiments (total N = 123), we found that 7- to 9-year-old children from the US (i) reason that people who are close will accurately represent each other's goals and desires and (ii) infer that people are socially close when they accurately predict each other's emotional states. These findings suggest that children reason flexibly about mental state attributions within close relationships.