The present experiments tested bilingual infants' developmental narrowing for the interpretation of sounds that form words. These studies addressed how language specialization proceeds when the environment provides varied and divergent input. Experiment 1 (N = 32) demonstrated that bilingual 14- and 19-month-olds learned a pair of object labels consisting of the same syllable produced with distinct pitch contours (rising and falling). Infants' native languages did not use pitch contour to differentiate words. In Experiment 2 (N = 16), 22-month-old bilinguals failed to learn the labels. These results conflict with the developmental trajectory of monolinguals, who fail to learn pitch contour contrasts as labels at 17-19 months (Hay, Graf Estes, Wang, & Saffran, 2015). Bilingual infants exhibited a prolonged period of flexibility in their interpretation of potential word forms.