Infant sensitivity to speaker and language in learning a second label

•We examined when infants of 19 months learn a second label for an object.•Infants learn a second object label, but do not generalize it to another speaker.•When the second label is in another language than the first label, infants generalize the label across speakers.•Infants also showed that they learn novel words in an unfamiliar language.

Two experiments examined when monolingual, English-learning 19-month-old infants learn a second object label. Two experimenters sat together. One labeled a novel object with one novel label, whereas the other labeled the same object with a different label in either the same or a different language. Infants were tested on their comprehension of each label immediately following its presentation. Infants mapped the first label at above chance levels, but they did so with the second label only when requested by the speaker who provided it (Experiment 1) or when the second experimenter labeled the object in a different language (Experiment 2). These results show that 19-month-olds learn second object labels but do not readily generalize them across speakers of the same language. The results highlight how speaker and language spoken guide infants’ acceptance of second labels, supporting sociopragmatic views of word learning.