Infants' perception of intonation categories

Frota, S. , Butler, J. , Correia, S. , Severino, C. & Vigario, M.

Universidade de Lisboa

Little is known about the developmental course of infants' perception of linguistic intonation, as previous studies on pitch contrasts have focused on the acquisition of lexical pitch (lexical pitch accent, as in Japanese, or lexical tone, as in Mandarin). Intonation languages (e.g., English, Portuguese) use pitch height, pitch direction and pitch timing to convey phrasal meanings, like sentence type and pragmatic distinctions. We investigated European Portuguese-learning infants' perception of two native pitch contrasts: the statement/yes-no question distinction, marked by a pitch direction contrast (falling/rising), and the broad/narrow focus distinction, signalled by a pitch timing contrast (early/late fall within the syllable). We asked (i) whether the developmental perceptual trajectory of the two contrast types was similar and (ii) how it related to previous reports on pitch perception by infants learning lexical pitch systems. Using a visual fixation procedure, we tested infants' discrimination of the statement/question contrast at 5-6 months and 8-9 months (Exp1) and of the broad/narrow focus contrast at 6-7 and 11-12 months (Exp2). Results from Exp1 showed successful discrimination for both age groups (n=38), whereas preliminary results from Exp2 suggest that only the older infants were able to discriminate the contrast (n=15). These results are in line with data from Proso-Quest, a parental report for the assessment of prosodic development in Portuguese infants/toddlers, showing an earlier development of question comprehension relative to narrow focus (respectively, 12 and 15 months; percentile 75, n=80). Our experimental findings suggest that the perceptual trajectory of intonation categories depends on the primary cues involved, supporting earlier results that show a protracted development of the perception of timing relative to pitch height/direction (Bion et al. 2011). Furthermore, our findings suggest that perception of intonation categories based on a pitch direction contrast may be as precocious as lexical tone perception (Yeung et al. 2012).