Not just if, but how much: Children and adults use cost and need to make evaluations about generosity across contexts.

Evaluations of others' generosity are critical for selecting quality social partners, yet the factors which systematically affect these evaluations and whether they vary across development are still relatively unclear. Here, we establish that two key dimensions adults and children (aged 4 to 7 years) consider are the cost associated with a giving action and the need of the recipient, through six pre-registered experiments with Canadian and U.S. American participants. Experiments 1 and 2 demonstrate that adults' and children's third-party evaluations of generosity are sensitive to variations in each factor, across several operationalizations of cost and need in both comparative and standalone contexts, suggesting cost and need can be spontaneously evoked. However, children's responses were more consistent for need scenarios than cost scenarios. In Experiments 3 and 4, we modified our scenarios to evaluate whether variations in cost and need are considered simultaneously in both generosity evaluations and affiliative preferences. Adults' and older children's (ages 6 to 7) evaluations of generosity and affiliative preferences were sensitive to both factors, but younger children did not utilize this information systematically. Importantly, in Experiments 5 and 6, adults' and older children's generosity evaluations were only sensitive to information about cost and need when the giver's actions conferred utility to a recipient, but not when actions were self-serving. Taken together, we establish robust evidence that cost and need are considered in generosity evaluations by demonstrating that Canadian and U.S. American adults and children utilize this information consistently, spontaneously, and simultaneously.