Young infants expect an unfamiliar adult to comfort a crying baby: Evidence from a standard violation-of-expectation task and a novel infant-triggered-video task.

Do infants expect individuals to act prosocially toward others in need, at least in some contexts? Very few such expectations have been uncovered to date. In three experiments, we examined whether infants would expect an adult alone in a scene with a crying baby to attempt to comfort the baby. In the first two experiments, 12- and 4-month-olds were tested using the standard violation-of-expectation method. Infants saw videotaped events in which a woman was performing a household chore when a baby nearby began to cry; the woman either comforted (comfort event) or ignored (ignore event) the baby. Infants looked significantly longer at the ignore than at the comfort event, and this effect was eliminated if the baby laughed instead of cried. In the third experiment, 8-month-olds were tested using a novel forced-choice violation-of-expectation method, the infant-triggered-video method. Infants faced two computer monitors and were first shown that touching the monitors triggered events: One monitor presented the comfort event and the other monitor presented the ignore event. Infants then chose which event they wanted to watch again by touching the corresponding monitor. Infants significantly chose the ignore over the comfort event, and this effect was eliminated if the baby laughed. Thus, across ages and methods, infants provided converging evidence that they expected the adult to comfort the crying baby. These results indicate that expectations about individuals' actions toward others in need are already present in the first year of life, and, as such, they constrain theoretical accounts of early prosociality and morality.