Chapter 7 Beyond Segments: How Children Acquire Prosody

1. Chapter 7Beyond Segments: How Children Acquire Prosody Margaret Kehoe

2. Introduction • Prosody plays a crucial role in language development • Infants are sensitive to prosodic characteristics of language even before birth • Interest in prosody has surged since the 1980’s and thrived with the arrival of widely accessible acoustic analysis software • Nonlinear phonology • Autosegmental phonology • Metrical phonology • Prosodic phonology • The aim of this chapter is to give a research-based overview • Early perceptual and productive prosody • Stress • Timing • Intonation • Atypical prosody in special populations • Autism spectrum disorder • Childhood apraxia of speech • Language impairment

3. Definition of Prosody: General Aspects Sidebar 7.1 The Prosody Elephant

4. Definition of Prosody: Functions and Effects Figure 7.1 Functions and effects of prosody

5. Definition of Prosody: Components • Three acoustic dimensions combine to create different prosodic systems: • Fundamental frequency (perceived as pitch) • Amplitude or intensity (perceived as loudness) • Duration (perceived as length) • Stress: stressed syllables are longer, louder, and/or higher-pitched than unstressed ones • Timing: syllable durations; pause durations • Phrase-final lengthening: the final syllable in an utterance is longer than the preceding ones • Rhythm: pattern of stressed and unstressed syllables in utterances • Intonation: pattern of fundamental frequency across words, phrases, and entire utterances

6. Figure 7.3 Acoustic display, including time waveform, spectrogram, and pitch contour of the word “Puppe” [ˈpʊpə] produced by a German-speaking girl, aged 2;0, with rising intonation. Figure 7.2 Acoustic display, including time waveform, spectrogram, and pitch contour of the word “Puppe” [ˈpʊpə] produced by a German-speaking girl, aged 2;0.

7. Figure 7.4 The prosodic hierarchy

8. Additional Terminology (1) Headedness of feet • Foot • Trochee (“picture,” “little,” German “Puppe”) • Iamb (“guitar,” “alone,” German “kaputt”)

9. Prosodic patterns in different languages • Stress-timed: syllable durations can vary; intervals between stressed syllables can contain variable numbers of unstressed syllables. Sounds like Morse code. • Examples: English, German • Syllable-timed: syllable durations are fairly uniform. Sounds like a machine gun. • Examples: Italian, French • Mora-timed: syllable durations depend on the number of moras (unit of syllable weight) • Example: Japanese

10. Prosodic Development:Perception • Newborns can discriminate between languages based on just the low-frequency content, thought to reflect the rhythmic characteristics of languages • Infants under 4 months are sensitive to lexical stress and intonation patterns • Newborns can distinguish between two languages based on rhythmic characteristics (stress-, syllable-, mora-timed) • Infants prefer their own ambient language over other languages • Infants prefer the exaggerated prosody of infant-directed speech (“motherese”)

11. Sidebar 7.2 Child-Directed Speech • Also referred to as “Motherese” • Short, simple sentences • Frequent repetitions • Words have one or two syllables • Higher pitch • Wider pitch range • Slower rate • Longer pauses • Increased final syllable lengthening

12. Sidebar 7.3 The Prosodic Bootstrapping Hypothesis • Infants use prosodic information to infer clausal and phrasal boundaries • Acoustic properties cue syntactic boundaries • Infants are sensitive to these properties • Infants use these cues in the processing of the speech stream • Empirical evidence: • Infants prefer artificial pauses at natural boundaries, not in the middle of the passage

13. Clausal and Phrasal Segmentation • Clausal and phrasal boundaries are marked by prosodic features such as heightened stress, changing intonational contours, pauses, and lengthening • Clause • Infants remember speech information better when it is packaged within a single prosodic unit instead of isolated words (Mandel, Jusczyk and Kemler Nelson, 1994) • Infants age 6 months can recognize a word sequence better when it is part of a well-formed clause instead of consisting of the last word of one clause and the first word of another (Nazzi, Kemler Nelson, Jusczyk, and Jusczyk, 2000) • Phrase • Infants age 6 months prefer passages containing a familiar phonological sequence when this sequence consists of a well-formed phrasal unit, compared to when it corresponds to a syntactic non-unit (Soderstrom et al., 2003)

14. Word Segmentation • Metrical segmentation strategy • German- and English-learning infants, age 6 and 9 months, respectively, prefer trochaic feet (strong-weak) over iambic ones (weak-strong) (Höhle, Bijeljac-Babic, Herold, Weissenborn & Nazzi, 2009; Jusczyk, Cutler & Redanz, 1993) • At 7.5 months, babies can segment trochaic words in a stream of speech and at 10.5 months, also iambic ones (Jusczyk, Houston, and Newsome, 1999)

15. Figure 7.5 Timeline of infant perception of prosody

16. Production Prelinguistic and early linguistic period • Ambient language effects • The babble productions of English and Swedish infants at age 10 to 18 months can not be distinguished by a group of expert listeners (Engstrand, Williams & Lacerda, 2003) – consistent with other studies that have failed to find an ambient language effect on babble • However, when rhythmic and intonational aspects are studied, ambient language effects can be observed • Newborn cries of German and French infants resemble the ambient language in pitch contour (Mampe, Friederici, Christophe & Wermke, 2009) • In reduplicated babble, French infants produce fewer falling intonational contours than English infants (Whalen, Levitt, & Wang, 1991) and a higher percentage of long final syllables (Levitt & Wang, 1991) • During the late babble and early word stages, ambient language effects are controversial at the 4-word stage (30-minute recording session with 4 different words) • At the 25-word stage, clear differences in intonational contours can be seen (included babble and speech) (Vihman, DePaolis and Davis, 1998)

17. Sidebar 7.4 Prosodic Regression • Some researchers have observed that infants appear to regress in their acquisition of prosody between age 10 months and the first word period • More level intonation after acquiring falling tones (Scollon, 1976) • Regression in phrase-final lengthening at the onset of first words (Levitt, 1993). • Could be due to (Snow & Balog, 2002) • More focus on segmental development • Reorganization of prosodic structures from biologically based to linguistically based

18. Pragmatic Differentiation Infants use prosodic tools to convey meaning from a very early age Infants 4 to 8 months use falling or level contours for discomfort cries and rising intonation for requests (D’Odorico, 1984) At 8 to 9 months, different intonation patterns are used for shared experiences, playing with toys, and cries for interventions (the latter with higher pitch and rising intonation) (D’Odorico and Franco, 1991) During the 1-word period, more rising tones are used for requests for interaction and more falling tones for those not calling for interaction (Halliday, 1975) As mean length of utterance (MLU) increases, contextual effects on prosody become more noticeable

19. Pragmatic Context • Expressing emotion • Longer duration, higher F0, lower intensity than during communicative interaction • Interacting • Shorter duration, higher F0, more variable F0 than during investigating • Rising tones • Investigating • Intermediate duration, lower F0, level F0 • Falling tones (Papaeliou, Minadakis, & Cavouras, 2002; Papaeliou & Trevarthen, 2006)

20. Transitional Phase between One- and Two-Word Utterances • Successive Single Word Utterances to two-word utterances: each word has its own • Primary stress • Unique intonational contour • Pause before/after the word • Two-word utterances • Integrated intonational contour • One primary stress • No pause between the words • These two utterance types can co-exist for a while

21. Key “.”= short pause, “-” and “—” = pauses of increasing length accents above vowels =falling and rising pitch contours capitalization indicates stress “/” = tone units or sense groups DÀDDY/ — ÈAT/ DÁDDY/ — ÈAT/ DÀDDY/ - ÈAT/ DÁDDY/ - ÈAT/ DÀDDY/ . ÈAT/ DÁDDY/ . ÈAT/ DÀDDY/ÈAT/ DÁDDY/ÈAT/ daddy ÈAT DÁDDY eat/ DÀDDY eat DÁDDY ÈAT/ • As children progress from one-word to two-word utterances, they create an intonational contour integrating the two words • Different ways to realize two-word combinations (Crystal, 1986) • Different types of word combinations are integrated in different ways and at different ages (Behrens & Gut, 2005)

22. Stress Lexical stress studied more intensively than phrasal stress During the early word period, children use all three parameters that adults use (pitch, duration, intensity), although there is great variability among children The earliest parameter to be controlled is pitch, followed by duration, then intensity

23. Stress Acquisition and Stress Errors Children make more errors on irregular versus regular stress forms, indicating that metrical structure and rules guide children’s acquisition of stress (Fikkert, 1994; Hochberg, 1988) Stress errors occur relatively rarely (Kehoe & Stoel-Gammon, 1997; Pollock et al., 1993; Prieto et al., 2011; Wijnen, Krikhaar, & Den Os, 1994) Some children may shift stress to syllables that are difficult to articulate (e.g., rhotacized vowels)

24. (4) Examples of stress errors in English in children aged 2;3 and 2;10 (from Kehoe, 1998; Kehoe & Stoel-Gammon, 1997)

25. (5) Examples of stress errors associated with rhotacized vowels (adapted from Kehoe, 1997, p.404).

26. 7S1 English-speaking children, aged 2;10, producing “crocodile,” “helicopter,” and “kangaroo” with correct and shifted stress 7S2 French-speaking boy, aged 2;9, producing bisyllabic words (“cheval ,“ “fantôme“) 7S3 French-speaking girl, aged 1;10, producing bisyllabic words (“biberon,“ “poisson,“ “tortue,“ “assiette“) 7S4 German-speaking girl, aged 2;6, producing bisyllabic words (“Puppe,” “Sonne,” “Walde”) 7S5 German-speaking boy, aged 2;6, producing bisyllabic words (“Hause,” “Henne”) 7S6 Spanish-speaking boy, aged 2;6, producing bisyllabic words (“barco,” “bota,” “corto,” “gato,” “grande,” “malo”)

27. Phrasal and Contrastive Stress (6) Seth using stress to mark new information (Examples taken from Wieman, 1976, p.286) Man. BLUE man. Ball. NICE ball. ORANGE ball. No sock. BLUE sock. • Children at the two-word stage are able to use stress to create contrast and emphasis • From age 2;9 to 4;6, children use contrastive stress to signal new information (Baltaxe, 1984; Hornby & Hass, 1970) • More prevalent when referring to subjects than verbs or objects

28. Compound Word versus Phrasal Stress (7) Compound vs. Phrasal Stress (Vogel & Raimy, 2002, p.228) • 2-year-old children can produce correct lexical stress in compound nouns, but the distinction between compound and phrasal stress develops later, well into the school years

29. (8) Examples of compound nouns and noun phrases

30. Production vs. Comprehension of Phrasal and Sentence stress • By age 4 years, children are competent users of phrasal and sentence stress • Their ability to interpret phrasal and sentence develops later, by 6 years of age • Asymmetry may relate to methodological differences • Comprehension tasks are more complex, e.g., disambiguating linguistic structures

31. Timing Rhythm • Stressed-timed languages have roughly equal intervals between stressed syllables (e.g., German, English) • Syllable-timed languages have syllables of roughly equal length (e.g., Spanish) • A better way to quantify syllabic durations: • In Ramus et al.’s (1999) approach, the duration of vocalic and consonantal intervals is submitted to three calculations: • the proportion of vocalic intervals within the sentence (%V), • the standard deviation of the duration of vocalic intervals (∆V), • the standard deviation of the duration of consonantal intervals (∆C), • Low et al. (2000): Pairwise Variability Index: differences in duration in any two successive pairs of intervals

32. By age 3 or 4, children show the rhythmic characteristics of their ambient language in terms of vocalic and consonantal durations (studies done in German, English, French, Cantonese) • Children learning a syllable-timed language show the rhythmic characteristics of the ambient language at an earlier age than children learning a stress-timed language

33. Phrase Final Lengthening (PFL) • The prolongation of the final syllable in a phrase • Not clear whether this is a biological phenomenon or has a linguistic basis • In a study of children in the one-word stage (age 1;0 to 1;8), Snow (1994) found that PFL declined in the middle of the study period and increased again, closely linked to the emergence of two-word utterances

34. Intonation • Intonation is the change in F0 across words, phrases, or longer utterances • In adult speech, it has many functions • Affective • Pragmatic • Grammatical • Children as young as 1;6 mark final syllables with falling tones

35. Functional Development of Intonation • Do children express pragmatic intent or emotion in their use of intonation? (Snow & Balog, 2002) • This distinction is often difficult to make • Here, the focus is on grammatical use of intonation • Clearly seen in utterance-final falling tone • Demonstrated by children age 1;6 and up

36. Proposed order of “tonal contrasts” in acquisition (Crystal, 1989): • Stage 1: falling tones • Stage 2: falling vs. level tones • Stage 3: falling vs. high rising tones • Stage 4: falling vs. high falling tones • Stage 5: rising vs. high rising tones • Stage 6: falling vs. high rising-falling tones • Stage 7: rising vs. falling-rising tones • Stage 8: Later contrasts, e.g., high vs. low rising-falling tones • Some empirical evidence for this has been found • Falling tones are acquired before rising tones • Simple (unidirectional) contours are acquired before complex (bidirectional) tones • There is great variability among children (Snow, 1995)

37. Are Falling Contours Less Marked than Rising Contours? • Yes • Physiological reasons: subglottal pressure declines at the end of an utterance • Falling contours are acquired earlier than rising contours (Snow, 2002) • Falling contours are less variable than rising tones (Snow & Stoel-Gammon, 1994) • Falling contours are substituted for rising contours (Lleó, Rakow, & Kehoe, 2004) • Falling contours are the most frequent contours at the 2-word stage (Behrens & Gut, 2005) • Perhaps not (Prieto et al., 2011) • More recent studies using the autosegmental-metrical (AM) approach to intonation show that young children are capable of producing more complex melodies than falling and rising contours • Falling contours are the predominant pattern in many of the languages studied suggesting a bias towards recording falling tones

38. Later Intonation Development Most studies on intonation focus on preschoolers, but intonational development continues into the school years In children age 5 through 13, production of intonation is acquired by age 5 years but comprehension of intonation continues to develop through age 10 and beyond (Wells, Peppé & Goulandris, 2004) This suggests that comprehension of intonation goes hand in hand with the development of syntactic structures

39. Sidebar 7.5 Late Intonation Cruttenden (1974) tested children’s ability to predict a soccer score based on the intonation of the announcer (“Liverpool three, Everton ?”). Of 28 boys, ages 7 to 10, only one could reliably predict whether the game ended in a draw, win, or loss for the home team

40. Cruttenden (1974)

41. Atypical Prosody • Can occur in children who are otherwise typically developing • Is frequently seen in children with certain clinical diagnoses such as autism spectrum disorder (ASD), childhood apraxia of speech (CAS), and specific language impairment (SLI)

42. Sidebar 7.6 Atypical Prosody in a Normally Developing Child 7S7 English-speaking child, aged 2;4, producing multisyllabic words (“alligator,” “elephant,” “potato,” “ avocado,” “helicopter,” “dinosaur,” “octopus,” “telephone”) with several examples of unusual prosodic patterns • Some normally developing children may display unusual prosodic patterns at certain times in development. In Kehoe & Stoel-Gammon’s (1997) study of English-speaking children’s multisyllabic productions, one child (28m2), aged 2;4, appeared to operate with an iambic template as shown in the examples below: • picture /ˈpɪktʃɚ/ [pɪkˈtʃɝ] • apple /ˈæpl͎/ [æˈboʊː] • banana /bəˈnænə/ [næˈnɑː] • Helicopter /ˈhɛləˌkɑptɚ/ [kæˈtʰɝ]

43. 7S8 Conversational speech of a boy, age 11, with a history of severe childhood apraxia of speech 7S9 Conversational speech of the identical twin brother of the boy in 7S9, also with a history of severe childhood apraxia of speech • Autism spectrum disorder • McCann and Peppé’s (2003 ) review of studies between 1980 and 2002 have reported contradictory results • Most consistent finding: difficulty with realization and placement of contrastive stress • More recent studies (Chevallier, Noveck, Happé & Wilson, 2009; Peppé, McCann, Gibbon, O’Hare, & Rutherford. 2007) show that affective and pragmatic functions are affected more than grammatical ones • Childhood apraxia of speech • Mostly deficits regarding lexical and phrasal stress

44. Specific language impairment • Children with SLI have greater difficulty using prosodic cues to infer grammatical rules in an artificial language, compared to children without SLI (Weinert, 1992) • Children with SLI tend to omit unstressed syllables more frequently than children without SLI (Bortolini & Leonard, 2000; Owen, Dromi, & Leonard, 2001) • Children with SLI display difficulty interpreting grammatical and pragmatic functions in receptive prosodic tasks

45. Connections Chapter 2: Tools for assessing prosody Chapter 18: More on childhood apraxia of speech and other motor speech disorders Chapter 19: More on autism spectrum disorder Chapter 20: Comprehensive assessment of children’s speech abilities

46. Concluding Remarks • This chapter covers various aspects of prosody in typically developing children as well as in certain disorders • Not covered in this chapter: • Phonological aspects of prosody • Interface of prosodic development with semantic, pragmatic, and grammatical development • Research investigating the acquisition of prosody is an expanding field.