Jan Charles‐Luce

An examination of similarity neighbourhoods in young children's receptive vocabularies.

Based on an analysis of similarity neighbourhoods of worlds in childrens lexicons, Dollaghan (1994) argues that because of the degree of phonological overlap among lexical items in memory, children must perform detailed acoustic-phonetic analyses in order to recognize spoken words. This is in contradiction to Charles-Luce & Luce (1990), who reported that the similarity neighbourhoods in younger childrens expressive lexicons are sparse relative to older childrens and adult lexicons and that young children may be able to use more global word recognition strategies. The current investigation re-examined these issues. Similarity neighbourhoods of young childrens receptive vocabularies were analysed for three-phoneme, four-phoneme and five-phoneme words. The pattern of the original results from Charles-Luce & Luce (1990) was replicated.

Representation of Lexical Form

The authors attempted to determine whether surface representations of spoken words are mapped onto underlying, abstract representations. In particular, they tested the hypothesis that flaps--neutralized allophones of intervocalic /t/s and /d/s--are mapped onto their underlying phonemic counterparts. In 6 repetition priming experiments, participants responded to stimuli in 2 blocks of trials. Stimuli in the 1st block served as primes and those in the 2nd as targets. Primes and targets consisted of English words containing intervocalic /t/s and /d/s that, when produced casually, were flapped. In all 6 experiments, reaction times to target items were measured as a function of prime type. The results provide evidence for both surface and underlying form-based representations.

Contextual effects on vowel duration, closure duration, and the consonant/vowel ratio in speech production

Acoustic measurements were conducted to determine the degree to which vowel duration, closure duration, and their ratio distinguish voicing of word-final stop consonants across variations in sentential and phonetic environments. Subjects read CVC test words containing three different vowels and ending in stops of three different places of articulation. The test words were produced either in nonphrase-final or phrase-final position and in several local phonetic environments within each of these sentence positions. Our measurements revealed that vowel duration most consistently distinguished voicing categories for the test words. Closure duration failed to consistently distinguish voicing categories across the contextual variables manipulated, as did the ratio of closure and vowel duration. Our results suggest that vowel duration is the most reliable correlate of voicing for word-final stops in connected speech.

The Effects of Semantic Context on Voicing Neutralization

The present study examined regressive voice assimilation in Catalan in an attempt to determine a systematic explanation of complete versus incomplete voicing neutralization. Two types of contexts were constructed. In one type, semantic information was present to bias the meaning of target words. In the other type, no semantic information was present. The results showed that vowel duration distinguished underlying voicing in the neutral context only. The results suggest that neutralization occurs when semantic information is present, but that a voicing contrast is realized when it is absent.

Representation of lexical form: evidence from studies of sublexical ambiguity.

The authors examined the role of intermediate, sublexical representations in spoken word perception. In particular, they tested whether flaps, which are neutralized allophones of intervocalic /t/s and /d/s, map onto their underlying phonemic counterparts. In 2 shadowing tasks, the authors found that flaps primed their carefully articulated counterparts, and vice versa. Because none of the flapped stimuli were lexically ambiguous (e.g., between rater and raider), these results provide evidence that such priming is sublexically mediated. Therefore, the current study provides further insights into when underlying form-based representations are activated during spoken word processing. In particular, the authors argue that phonological ambiguity, inherent in their flapped stimuli, is one of the conditions leading to the activation of underlying representations.

Word‐final devoicing in German and the effects of phonetic and sentential contexts

The present study investigated the possible effects that place of articulation of the final stop, the phonetic environment of the target word, and sentential position might have on vowel duration, voicing into closure, and closure duration as acoustic correlates of underlying voicing. The results of the study replicate the findings that word‐final devoicing is non‐neutralizing in German. However, the results also show that the temporal correlates of underlying voicing are different for dental and velar stops and are different for lexical items. Moreover, for the dental stops, vowel duration, and voicing into closure as correlates of underlying voicing are not independent of phonetic or sentential contexts. The overall results suggest that the phonetic rules necessary to implement word‐final stops in German must be sensitive to place of articulation, surrounding phonetic and sentential contexts, and even individual lexical items. [Supported by NIH Training Grant T32 NS‐7134.]

Perception of word‐final voicing in two sentence contexts

Stressed syllables produced before major syntactic boundaries typically exhibit a marked lengthening, suggesting that listeners may have expectations regarding the relative length of syllables occurring immediately before a major syntactic boundary. We investigated the possible consequences of such expectations for the perception of word‐final stop voicing, which may be cued by vowel and/or closure duration. We examined labeling performance for two continua of synthetic stop‐vowel‐stop words varying in vowel and closure duration. These continua were embedded in synthetic, monotone sentences in which the target stimuli occurred either at the end of an initial subordinate clause or one word before a clause boundary. For half of stimuli, a pause occurred at the boundary; for the other half, no pause occurred. Expectation of phrase‐final lengthening produced a large effect on labeling performance, but only when a pause occurred at the clause boundary. The implications of these findings for perception of voici...

Temporal processing and phonotactic probability in spoken word recognition

This study examined the influence of phonotactic information on spoken language recognition in adults. Subjects performed a lexical decision task on 120 phonotactically legal bisyllablic CVCCVC nonsense words that varied in their phonotactic probability and primary stress placement. Subjects responded faster to nonsense words containing low probability initial syllables and slower to nonsense words containing high‐probability initial syllables. On the other hand, subjects responded faster to nonsense words containing high probability final syllables and slower to nonsense words containing low‐probability final syllables. Our results suggest that two phonotactically based processes may be used during word recognition. The first process is a winnowing of candidate words based on their phonotactic probability. The second process is a confirmatory process in which the lexical status of the sole candidate is confirmed based on the phonotactic probability of the item. [Work supported by NIH‐NIDCD.]

Spoken word recognition in older adults: Activation and decision

Spoken word recognition may be characterized by two successive stages: (1) activation of multiple form‐based representations in memory and (2) frequency‐biased perceptual decision. Recent research has suggested that older adults show deficits in controlled processing in perceptual and memory tasks, suggesting that while activation mechanisms subserving spoken word recognition may remain relatively intact over time, perceptual decision processes degrade. In order to investigate the possible loci of older adults’ recognition difficulties, perception of specially selected words that orthogonally varied on three dimensions was examined: word frequency, neighborhood density, and neighborhood frequency. Effects of neighborhood density are typically associated with activation mechanisms, whereas neighborhood frequency is associated with perceptual decision. The implications of these results for theories of aging and spoken word recognition will be discussed. [Work supported by grants from NIDCD.]

Assimilatory versus nonassimilatory neutralization processes in Catalan

In general, phonologists claim that neutralization results in the acoustic‐phonetic obliteration of an underlying phonemic contrast in favor of one the members of the contrast. For Catalan, two possible processes are involved in the neutralization of underlying voicing in word‐final stops: (1) word‐final devoicing, and (2) regressive voice assimilation. In the latter case, word‐final stops are realized as either voiced or voiceless depending upon the voicing of the following phonetic segment. However, in the former case, word‐final stops are always realized as voiceless in those environments that do not overlap with regressive voice assimilation. In the present investigation, native Catalan speakers produced monosyllabic minimal pairs differing in the underlying voicing of the final stop in two nonassimilatory environments and in two assimilatory environments. Vowel duration preceding the final stop, voicing during closure, and closure duration of the final stop were measured as acoustic correlates of voi...