Amanda C. Walley

Spoken Vocabulary Growth: Its Role in the Development of Phoneme Awareness and Early Reading Ability.

In this paper, two theoretical positionsregarding the developmental origins of thephoneme as a unit for lexical representationand processing are outlined – theaccessibility and emergent positions. OurLexical Restructuring Model (Metsala & Walley1998), which is consistent with the secondposition, focuses on the role of vocabularygrowth in prompting the implementation of morefine-grained, segmental representations forlexical items in childhood; this restructuringis viewed as an important precursor to theexplicit segmentation or phoneme awarenessskills implicated in early reading success.Empirical evidence that supports this model issummarized, including preliminary results fromone of our most recent studies. Severalsuggestions are made for future research thatwill lead to a better understanding of thedevelopment of spoken word recognition and thelinks between speech- and reading-relatedabilities.

Discrimination of relative onset time of two‐component tones by infants

A great deal of research has focused on the perception of voice onset time (VOT) differences in stop consonants. Yet, the nature of the mechanisms responsible for the perception of these differences is still the subject of much debate. Recently Pisoni [J. Acoust. Soc. Am. 61, 1352-1361 (1977)] has presented evidence which suggested that the perception of VOT differences by adult listeners may reflect a basic limitation on processing temporal order information by the auditory system. For adults, stimuli with onset differences approximately greater than 20 ms are perceived as successive events (either leading or lagging), while stimuli with onset differences less than about 20 ms are perceived as simultaneous events. Thus, differences in voicing may have an underlying perceptual basis in terms of three well-defined temporal attributes corresponding to leading, lagging, or simultaneous events at onset. The present experiment was carried out to determine whether young infants can discriminate differences in temporal order information in nonspeech signals and whether their discimination performance parallels the earlier data obtained with adults. Discimination was measured with the high-amplitude sucking (HAS) procedure. The results indicated that infants can disciminate differences in the relative onset of two events; the pattern of discrimination also suggested the presence of three perceptual categories along this temporal continuum although the precise alignment of these categories differed somewhat from the values found in the earlier study with adults.

The growth of lexical constraints on spoken word recognition

In this study, we examined the influence of various sources of constraint on spoken word recognition in a mispronunciation-detection task. Five- and 8-year-olds and adults were presented with words (intact or with word-initial or noninitial errors) from three different age-of-acquisition categories. “Intact” and “mispronounced” responses were collected for isolated words with or without a picture referent (Experiment 1) and for words in constraining or unconstraining sentences (Experiment2). Some evidence for differential attention to word-initial as opposed to non-initial acoustic-phonetic information (and thus the influence of sequential lexical constraints on recognition) was apparent in young children’s and adults’ response criteria and in older children’s and adults’ reaction times. A more marked finding, however, was the variation in subjects’ performance, according to several measures, with age and lexical familiarity (defined according to adults’ subjective age-of-acquisition estimates). Children’s strategies for responding to familiar and unfamiliar words in different contexts are discussed.

THE GATING PARADIGM: EFFECTS OF PRESENTATION FORMAT ON SPOKEN WORD RECOGNITION BY CHILDREN AND ADULTS

This study focused on the impact of stimulus presentation format in the gating paradigm with age. Two presentation formats were employed—the standard, successive format and a duration-blocked one, in which gates from word onset were blocked by duration (i.e., gates for the same word were not temporally adjacent). In Experiment 1, the effect of presentation format on adults’ recognition was assessed as a function of response format (written vs. oral). In Experiment 2, the effect of presentation format on kindergarteners’, first graders’, and adults’ recognition was assessed with an oral response format only. Performance was typically poorer for the successive format than for the duration-blocked one. The role of response perseveration and negative feedback in producing this effect is considered, as is the effect of word frequency and cohort size on recognition. Although the successive format yields a conservative picture of recognition, presentation format did not have a markedly different effect across the three age levels studied. Thus, the gating paradigm would seem to be an appropriate one for making developmental comparisons of spoken word recognition.

Evidence for phonetic processing of cues to place of articulation: Perceived manner affects perceived place

Using stimuli that could be labeled either as stops [b,d] or as fricatives [f,v,θ,ð], we found that, for a given acoustic stimulus, perceived place of articulation was dependent on perceived manner. This effect appeared for modified natural syllables with a free-identification task and for a synthetic transition continuum with a forced-choice identification task. Since perceived place could be changed by changing manner labels with no change in the acoustic stimulus, it follows that the processing of the place feature depends on the value the listener assigns to the manner feature rather than directly on any of the acoustic cues to manner. We interpret these results as evidence that the identification of place of articulation involves phonetic processing and could not be purely auditor

Adults' perception of native and nonnative vowels: Implications for the perceptual magnet effect

Two experiments were conducted to evaluate the perceptual magnet effect. In Experiment 1, Amer-ican English speakers representing diverse dialects were presented with a fine-grained set of stimuli (varying in just noticeable differences forF1 andF2) and indicated whether they heard “/i/” or “not /i/,” thus delimiting the /i/ portion of the vowel space for individual subjects. Then these same subjects selected their own /i/ prototype with a method-of-adjustment procedure. The data from this experiment were used to synthesize customized prototype and nonprototype stimulus sets for Experiment 2. In Experiment 2,24 of our original 37 subjects completed a discrimination task for each of three conditions, in which vector stimuli varied from the subject’s prototype, the nonprototype, or a foreign vowel (/y/) in 15-mel steps. Subjects displayed higher discrimination, as indexed byd′, for the nonprototype condition than they did for both the prototype and the foreign conditions. In addition, discrimination was better for variants further away from the referent in each condition. However, discrimination was not especially poor for stimuli close to subjects’ individual prototypes—a result that would have yielded the strongest support for the operation of a magnet effect. This negative finding, together with other aspects of our results, raises problems for any theory of vowel perception that relies solely on “one-size-fits-all” prototype representations.

Children's spoken word recognition and contributions to phonological awareness and nonword repetition: A 1-year follow-up

This study examined effects of lexical factors on childrens spoken word recognition across a 1-year time span, and contributions to phonological awareness and nonword repetition. Across the year, children identified words based on less input on a speech-gating task. For word repetition, older children improved for the most familiar words. There was a competition effect for the word repetition task, but this effect was present only for the most familiar words on the gating task. Recognition for words from sparse neighborhoods predicted phonological awareness 1 year later, and children poorer at recognizing these words in Year 1 scored lower on word reading in Year 2. Spoken word recognition also accounted for unique variance in nonword repetition across the 1-year time span. Findings are discussed in terms of understanding the effects of vocabulary growth on spoken word recognition, phonological awareness, and nonword repetition.

Effects of lexical status on children’s and adults’ perception of native and non‐native vowels

Monolingual, English‐speaking 5‐year‐olds, 9‐year‐olds, and adults heard stimuli from two ‘‘native,’’ synthetic continua, in which the vowels ranged from English /i/ to /i/ in the context /b—b/ or /b—p/. Thus the endpoints of the first continuum constituted a word and a nonword (‘‘bib’’ vs *‘‘beeb’’); the reverse held for the second continuum (*‘‘bip’’ vs ‘‘beep’’). Other subjects heard stimuli from two ‘‘foreign’’ continua, where the vowels ranged from English /i/ to a foreign vowel /y/ in the contexts described above. Thus the endpoints of the first continuum corresponded to a word and a nonword (‘‘bib’’ vs *‘‘bYb’’); both endpoints of the second continuum corresponded to nonwords (*‘‘bip’’ vs *‘‘bYp’’). After training on endpoints, subjects’ identifications of the nine stimuli of a given continuum were examined to assess whether: children, like adults, exhibit a ‘‘lexical bias’’ effect for familiar vowels (from the ‘‘native’’ continua); vowel categories not bounded by another native vowel (as in the ‘‘...

Infant discrimination of two- and five-formant voiced stop consonants differing in place of articulation

According to recent theoretical accounts of place of articulation perception, global, invariant properties of the stop CV syllable onset spectrum serve as primary, innate cues to place of articulation, whereas contextually variable formant transitions constitute secondary, learned cues. By this view, one might expect that young infants would find the discrimination of place of articulation contrasts signaled by formant transition differences more difficult than those cued by gross spectral differences. Using an operant head-turning paradigm, we found that 6-month-old infants were able to discriminate two-formant stimuli contrasting in place of articulation as well as they did five-formant + burst stimuli. Apparently, neither the global properties of the onset spectrum nor simply the additional acoustic information contained in the five-formant + burst stimuli afford the infant any advantage in the discrimination task. Rather, formant transition information provides a sufficient basis for discriminating place of articulation differences.

A developmental study of native and non‐native vowel perception

Two vowel continua were created using the Klatt synthesizer. F1 frequency varied in the same eight equal mel steps in both. F2 frequency also varied in eight equal mel steps but, whereas it increased relative to /i/ in one continuum, it decreased relative to /i/ in the other. As a result, vowels in the ‘‘native–native’’ continuum ranged from /i/ to /i/, those in the native‐foreign continuum from /i/ to a vowel symbolized as /Y/. Adults and children ranging in age from 4 to 12 years (ten per group) were trained to identify the endpoints of both continua as either /i/ or ‘‘the other vowel.’’ There was no effect of subjects’ age on the number of stimuli identified as /i/. This failed to support the hypothesis that vowels not bounded by another native language category−such as /i/ in the /i/–/Y/ but not the /i/–/i/ continuum−will expand outward with age. Slope analyses revealed that the 4‐ to 6‐year‐old children had shallower identification functions than the adults. Much the same effect of age was evident fo...