Melissa A. Redford

The relative perceptual distinctiveness of initial and final consonants in CVC syllables

Among the worlds languages, syllable inventories allowing only initial consonants predominate over those allowing both initial and final consonants. Final consonants may be disfavored because they are less easy to identify and/or more difficult to produce than initial consonants. In this study, two perceptual confusion experiments were conducted in which subjects identified naturally produced consonant-vowel-consonant syllables in different frame sentences. Results indicated that initial consonants were significantly more identifiable than final consonants across all conditions. Acoustic analyses of the test syllables indicated that the relative identifiability of initial and final consonants might be explained in terms of production differences as indicated by the greater acoustic distinctiveness of initial consonants.

Constrained Emergence of Universals and Variation in Syllable Systems

A computational model of emergent syllable systems is developed based on a set of functional constraints on syllable systems and the assumption that language structure emerges through cumulative change over time. The constraints were derived from general communicative factors as well as from the phonetic principles of perceptual distinctiveness and articulatory ease. Through evolutionary optimization, the model generated mock vocabularies optimized for the given constraints. Several simulations were run to understand how these constraints might define the emergence of universals and variation in complex sound systems. The predictions were that(1) CV syllables would be highly frequent in all vocabularies evolved under the constraints; (2) syllables with consonant clusters, consonant codas,and vowel onsets would occur much less frequently; (3) a relationship would exist between the number of syllable types in a vocabulary and the average word length in the vocabulary; (4) different syllable types would emerge according to, what we termed, an iterative principle of syllable structure and their frequency would be directly related to their complexity; and(5) categorical differences would emerge between vocabularies evolved under the same constraints. Simulation results confirmed these predictions and provided novel insights into why regularities and differences may occur across languages. Specifically, the model suggested that both language universals and variation are consistent with a set of functional constraints that are fixed relative to one another. Language universals reflect underlying constraints on the system and language variation represents the many different and equally-good solutions to the unique problem defined by these constraints.

The role of juncture cues and phonological knowledge in English syllabification judgments

Abstract Listener syllabification judgments vary on words with VCCV sequences. This variability seems to present a challenge to phonological theory, which predicts invariant behavior following from rules or principles. Judgment variability might be better accounted for by positing that syllable production and perception are linked by the signal. According to such a hypothesis, variable listener judgments would result from variable speaker productions. To determine whether phonological or phonetic factors better account for listener syllabification judgments, different speakers produced nonsense words, listeners syllabified them, and then stimuli characteristics were used to predict syllabification. Results showed that, in spite of production variability, listener judgments were nearly invariant on words with medial sequences that formed illegal onset clusters to the second syllable and on words with first syllable stress, suggesting that these tokens were syllabified according to categorical phonological knowledge. Other judgments could not be similarly explained, but instead were best predicted by gradient phonetic patterns cuing juncture. The results disconfirm the hypothesis that syllable production and perception are directly linked via the signal. Instead, they suggest a two-step model of English syllabification in which listeners rely on juncture cues to determine syllable boundaries only after phonological knowledge fails to indicate a unique boundary location.

A Comparative Analysis of Pausing in Child and Adult Storytelling

The goals of the current study were (1) to assess differences in child and adult pausing, and (2) to determine whether characteristics of child and adult pausing can be explained by the same language variables. Spontaneous speech samples were obtained from ten 5-year-olds and their accompanying parent using a storytelling/retelling task. Analyses of pause frequency, duration, variation in durations, and pause location indicated that pause time decreased with retelling, but not with age group except when child and adult pausing was considered in its speech and language context. The results suggest that differences in child and adult pausing reflect differences in child and adult language, not in the cognitive resources allocated to language production.

Unifying speech and language in a developmentally sensitive model of production

Speaking is an intentional activity. It is also a complex motor skill; one that exhibits protracted development and the fully automatic character of an overlearned behavior. Together these observations suggest an analogy with skilled behavior in the non-language domain. This analogy is used here to argue for a model of production that is grounded in the activity of speaking and structured during language acquisition. The focus is on the plan that controls the execution of fluent speech; specifically, on the units that are activated during the production of an intonational phrase. These units are schemas: temporally structured sequences of remembered actions and their sensory outcomes. Schemas are activated and inhibited via associated goals, which are linked to specific meanings. Schemas may fuse together over developmental time with repeated use to form larger units, thereby affecting the relative timing of sequential action in participating schemas. In this way, the hierarchical structure of the speech plan and ensuing rhythm patterns of speech are a product of development. Individual schemas may also become differentiated during development, but only if subsequences are associated with meaning. The necessary association of action and meaning gives rise to assumptions about the primacy of certain linguistic forms in the production process. Overall, schema representations connect usage-based theories of language to the action of speaking.

The perceived clarity of children's speech varies as a function of their default articulation rate

The current study investigated whether variation in childrens default articulation rate might reflect individual differences in the development of articulatory timing control, which predicts a positive correlation between rate and perceived clarity (motor skills hypothesis), or whether such variation is better attributed to speech external factors, which predicts that faster rates result in poorer target attainment (undershoot hypothesis). Two different speech samples were obtained from 54 typically developing children (5;2 - 7;11). Six utterances were extracted from each sample and measured for articulation rate and segmental duration. Fourteen adult listeners rated the utterances for clarity (enunciation). Acoustic correlates of perceived clarity, pitch, and vowel quality were also measured. The findings were that age-dependent and individual differences in childrens default articulation rates were due to segmental articulation and not to suprasegmental changes. The rating data indicated that utterances produced at faster rates were perceived as more clearly articulated than those produced at slower rates, regardless of a childs age. Vowel quality measures predicted perceived clarity independently of articulation rate. Overall, the results support the motor skills hypothesis: Faster default articulation rates emerge from better articulatory timing control.

Word-internal versus word-peripheral consonantal duration patterns in three languages

Segmental duration patterns have long been used to support the proposal that syllables are basic speech planning units, but production experiments almost always confound syllable and word boundaries. The current study tried to remedy this problem by comparing word-internal and word-peripheral consonantal duration patterns. Stress and sequencing were used to vary the nominal location of word-internal boundaries in American English productions of disyllabic nonsense words with medial consonant sequences. The word-internal patterns were compared to those that occurred at the edges of words, where boundary location was held constant and only stress and sequence order were varied. The English patterns were then compared to patterns from Russian and Finnish. All three languages showed similar effects of stress and sequencing on consonantal duration, but an independent effect of syllable position was observed only in English and only at a word boundary. English also showed stronger effects of stress and sequencing across a word boundary than within a word. Finnish showed the opposite pattern, whereas Russian showed little difference between word-internal and word-peripheral patterns. Overall, the results suggest that the suprasegmental units of motor planning are language-specific and that the word may be more a relevant planning unit in English.

Lexical and Phrasal Prominence Patterns in School-Aged Children's Speech

This study investigated the integration of word- and phrase-level prominences in speech produced by twenty-five school-aged children (6;2 to 7;3) and twenty-five adults. Participants produced disyllabic number words in a straight count condition and in two phrasal conditions, namely, a stress clash and non-clash phrasal context. Duration and amplitude measures of syllable rhymes were used to assess the realization of lexical stress, and fundamental frequency (F0) measures were used to assess the realization of phrasal pitch accents across conditions. Results showed that the duration and F0 correlates varied independently of each other as a function of condition in child speech, but much less so in adult speech. The group differences were taken to indicate that six-year-old children have yet to develop prosodic structures with integrated prominence. Structural and pragmatic interpretations of the results are discussed.

The relative perceptibility of initial and final consonants

Syllable inventories allowing only initial consonants predominate over those allowing both initial and final consonants in the world’s languages. One possible explanation may be that final consonants are less perceptually salient than initial consonants. In this study the perceptibility of final consonants was examined relative to initial consonants. The relative perceptibility of final consonants preceding word initial consonants compared with those preceding word initial vowels was also examined. Fourteen subjects were presented with 147 different nonsense CVC syllables spoken by four talkers in two frame sentences in −15 dB S/N. Subjects were asked to write down the nonsense syllable that occurred in each frame sentence. Results indicated that initial consonants were significantly more perceptible than final consonants (p=0.0002) and that final consonants which preceded a word initial vowel were significantly more perceptible than those that preceded a word initial consonant (p=0.0001). Subsequent anal...

Children's Abstraction and Generalization of English Lexical Stress Patterns

The current study investigated school-aged childrens internalization of the distributional patterns of English lexical stress as a function of vocabulary size. Sixty children (5;3 to 8;3) participated in the study. The children were asked to blend two individually presented, equally stressed syllables to produce disyllabic nonwords with different resulting structures in one of two frame sentences. The frame sentences were designed to elicit either a noun or verb interpretation of the nonword. Childrens receptive vocabulary was also assessed. The results indicated that children more readily blended syllable pairs that resulted in trochaic-compatible word structures than in iambic-compatible structures. This effect was strongest in young children with large vocabularies. As for stress placement, all children were sensitive to the effect of word structure, but only children with the largest vocabularies were sensitive to the biasing effect of grammatical category (noun = trochee; verb = iamb). The study results are discussed with reference to the observation that speech motor skills develop in tandem with lexical acquisition and the hypothesis that phonological knowledge emerges in part from abstraction across lexical representations.