The development of infants' use of novel verbal information when reasoning about others' actions.

How sophisticated are infants at using novel verbal information when reasoning about which of two objects an agent is likely to select? The present research examined the development of infants' ability to interpret a change from one novel word to another as signaling a possible change in which object the agent would choose next. In three experiments, 7- and 12-month-olds were familiarized to an event in which they heard a novel word ("A dax!") and then saw an agent reach for one of two distinct objects. During test, the infants heard a different novel word ("A pilk!") and then saw the agent grasp the same object or the other object. At 7 months, infants ignored the change in word and expected the agent to continue reaching for the same object. At 12 months, however, infants attended to the change in word: They realized that it signaled a possible change in the agent's upcoming actions, though they were unable to form a specific expectation about what these new actions might be, most likely due to their limited mutual-exclusivity assumption. Control conditions supported these interpretations. Together, these results suggest that by 12 months of age, infants understand not only that words are selected for communicative purposes, but also that a change from one novel word to another may signal a change in an agent's upcoming actions.