English-Learning Infants’ Developing Sensitivity to Intonation Contours

In four experiments, we investigated when and how English-learning infants perceive intonation contours that signal prosodic units. Using visual habituation, we probed infants’ ability to discriminate disyllabic sequences with a fall versus a rise in pitch on the final syllable, a salient cue used to distinguish statements from questions. First, we showed that at 8 months, English-learning infants can distinguish statement falls from question rises, as has been reported previously for their European Portuguese-learning peers who have extensive experience with minimal pairs that differ just in pitch rises and falls. Next, we conducted three experiments involving 4-month-olds to determine the developmental roots of how English-learning infants begin to tune into these intonation contours. In Experiment 2, we showed that unlike 8-month-olds, monolingual English-learning 4-month-olds are unable to distinguish statement and question intonation when they are presented with segmentally varied disyllabic sequences. Monolingual English-learning 4-month-olds only partially succeeded even when tested without segmental variability and a sensitive testing procedure (Experiment 3). When tested with stimuli that had been resynthesized to remove correlated duration cues as well, 4-month-olds demonstrated only partial success (Experiment 4). We discuss our results in the context of extant developmental research on how infants tune into linguistically relevant pitch cues in their first year of life.