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LINGUISTIC VARIABILITY AND YOUNG CHILDREN'S ACQUISITION OF PROSODIC SPEECH

TIMING

David Snow

Department of Speech and Hearing Sciences

University of Arizona

Tucson, AZ 85721

This paper focuses on English-speaking children's expressive prosody

during the period of early meaningful speech (18 to 24 months), with special

attention to two near universals of speech prosody - the falling tone contour

of intonation and final syllable lengthening (FSL). The studies reported here

present evidence about linguistic and developmental characteristics that are

associated with the acquisition of FSL by infants and toddlers.

Data for nine children were collected longitudinally over a period that

spanned three stages of linguistic development: single words (18 months),

beginning of word combinations (21 months), and the end of the two-word period

(24 months). The study shows that falling intonation is already stable in

infant speech during the period of single word utterances.

However, FSL showed a more complex, U-shaped curve type of development.

That is, there was a trend towards FSL in the speech of infants that

disappeared at the time the children were making the transition to

combinatorial speech. Then at the end of the two-word period FSL reemerged,

this time as a more consistent feature of the children's speech.

Two important implications for acquisition are discussed. First, the

study shows that FSL in English is stable in child speech at a later

developmental stage than intonation. This dissociation between FSL and

intonation suggests that FSL is not merely a secondary result of intonation

skills. Second, the relatively late emergence of FSL in English contrasts with

French, where FSL (like intonation) is stable by about 16 months. It is argued

that the crosslanguage difference in prosodic development reflects the

different pattern of prosodic speech timing in French versus English. In

French, the timing of segments is related only to word position, whereas in

English it is affected (among other features) by variable stress as well as

phrase position. It is concluded that the greater variability of speech timing

in English adult speech as compared with French affects the child's

acquisition of speech timing features.

Data are also presented concerning children's development of voice onset

time (VOT) in English during this period. VOT reflects a segmental aspect of

speech timing, namely, one that is determined largely by lexical

specifications, which can thus be expected to be less variable than

suprasegmental features like FSL which are specified entirely by the

linguistic context. The results show that VOT is acquired earlier than FSL.

These data comparing VOT and FSL in English are consistent with the

crosslanguage data comparing FSL in English and French, in that they suggest

that linguistic patterns and variability significantly affect the child's

acquisition of different speech timing skills.

Lastly, given the association between FSL and syntactic structure of

utterances, the acquisition evidence suggests that children's learning of suprasegmental features like FSL may be closely linked to their learning of

syntactic patterns as well. The findings are at least consistent with the

hypothesis that prosodic boundary features are, in part, a phonological

expression of the children's emerging grammar.