How do infants and adults process communicative events in real time?

Speech allows humans to communicate and to navigate the social world. By 12 months, infants recognize that speech elicits appropriate responses from others. However, it is unclear how infants process dynamic communicative scenes and how their processing abilities compare with those of adults. Do infants, like adults, process communicative events while the event is occurring or only after being presented with the outcome? We examined 12-month-olds' and adults' eye movements as they watched a Communicator grasp one (target) of two objects. During the test event, the Communicator could no longer reach the objects, so she spoke or coughed to a Listener, who selected either object. Infants' and adults' patterns of looking to the actors and objects revealed that both groups immediately evaluated the Communicator's speech, but not her cough, as communicative and recognized that the Listener should select the target object only when the Communicator spoke. Furthermore, infants and adults shifted their attention between the actors and the objects in very similar ways. This suggests that 12-month-olds can quickly process communicative events as they occur with adult-like accuracy. However, differences in looking reveal that 12-month-olds process slower than adults. This early developing processing ability may allow infants to learn language and acquire knowledge from communicative interactions.