Relating Intonational Pragmatics to the Pitch Realizations of Highly Frequent Words in English Speech to Infants

Relating Intonational Pragmatics to the Pitch Realizations of Highly Frequent Words in English Speech to Infants Carolyn M. Quam (cquam@psych.upenn.edu) Department of Psychology, University of Pennsylvania 3401 Walnut Street 408C, Philadelphia, PA 19104-6228 Jiahong Yuan (jiahong@babel.ling.upenn.edu) Department of Linguistics, University of Pennsylvania 619 Williams Hall, Philadelphia, PA 19104-6305 Daniel Swingley (swingley@psych.upenn.edu) Department of Psychology, University of Pennsylvania 3401 Walnut Street 411C, Philadelphia, PA 19104-6228 Abstract Infant-directed speech (IDS) is characterized by exaggerated intonation patterns and short, simple phrases. Because these exaggerated intonation patterns frequently convey a small, stereotyped range of emotional signals, we might expect particular words, like good or no, to be realized with consistent pitch contours. This consistency in a word’s pitch realization might facilitate word recognition, but in an intonation language like English, it could falsely suggest lexical tones, i.e., pitch variation signaling lexical contrast. The present work examines the speech input to the English- learning child to identify the amount, nature, and sources of pitch variation across about 3,300 tokens of 8 highly frequent words. We find two basic results. First, although intonation in IDS is prototypically exaggerated, about half the instances of frequently occurring, utterance-final words were flat in contour. Second, although each frequent word varied substantially in its intonation contours (e.g., rises versus rise- falls), there were large differences among words that seem to reflect the pragmatic categories typical of each word’s use. For instance, no was generally flat or falling, and consistently low in pitch, reflecting its occurrence in prohibitive utterances; while good occurred more often with a rise-fall contour, reflecting its approbational meaning. Even the word good, however, still had more flat contours than rise-fall contours. This within-word variability in pitch realization could help the child rule out lexical tone as contrastive in English. Keywords: intonation; prosody; infant-directed speech. Introduction Pitch is exploited in social interactions across the animal kingdom. Because larger organisms tend to produce lower sounds, many species use low or steeply falling pitch as an expression of dominance, and higher pitch for submissiveness or uncertainty (Ohala, 1994). Ohala (1984) argues that languages often capitalize on this link to express certainty (e.g., statements) through falling or low intonation, and uncertainty (e.g., questions) through high or rising intonation. Pitch also plays an important role in early human development. The distinctive pitch characteristics of infant- directed speech (IDS) complement the infant’s developing auditory system; the higher fundamental frequency (F0) mean and wider F0 range make the speech more interesting and easier for the developing auditory system to tune in to (Fernald, 1992). Infants prefer listening to IDS over adult- directed speech (ADS; Fernald, 1985), a preference driven primarily by IDS’s pitch characteristics (Fernald & Kuhl, 1987; Katz, Cohn, & Moore, 1996). Pragmatic functions of speech are expressed more clearly in IDS than in ADS. Fernald (1989) elicited utterances from mothers, intended to (1) get their infant’s attention, (2) show approval, (3) comfort the infant, or (4) prohibit the infant from touching an object. Comforting utterances and prohibitions were both low in pitch and falling, but prohibitions fell more sharply and were shorter and higher in amplitude. Attention-getting and approving utterances both had high mean F0 and a large F0 range, but attention-getting utterances were higher in amplitude. Considering the clarity of intonational meaning in IDS, it’s not surprising that infants respond to the emotional information conveyed by pitch variation before they know many words (Moore, Spence, & Katz, 1997). In spite of the early importance of intonation for capturing infants’ attention and conveying emotions and intentions, infants learning English must disregard lexical pitch in order to successfully learn and recognize words. By 9 months, English learners fail to discriminate a Thai lexical tone contrast (Mattock et al., 2007). And by 30 months, English learners know that pitch cannot distinguish words in English (Quam & Swingley, 2007). But figuring this out could be difficult if the intonational and syntactic simplicity of IDS leads highly frequent words to be realized with one consistent pitch contour. Is this the case for English? To answer this question, we examine the pitch contours of highly frequent words in mothers’ speech to their preverbal infants. By measuring the F0 characteristics of these words across tokens, we attempt to determine how the pitch structure of English conveys the lack of lexical tones. We might expect the pitch patterns across tokens of words to be more variable in English than in a lexical-tone language, where the pitch contour is specified in the word representation. The amount of variability across tokens could thus tell the infant which type of language she is learning. Knowing whether the pitch realizations of words