Planning and articulation in incremental word production: syllable-frequency effects in English

We investigated the role of syllables during speech planning in English by measuring syllable-frequency effects. So far, syllable-frequency effects in English have not been reported. English has poorly defined syllable boundaries, and thus the syllable might not function as a prominent unit in English speech production. Speakers produced either monosyllabic (Experiment 1) or disyllabic (Experiment 2-4) pseudowords as quickly as possible in response to symbolic cues. Monosyllabic targets consisted of either high- or low-frequency syllables, whereas disyllabic items contained either a 1st or 2nd syllable that was frequency-manipulated. Significant syllable-frequency effects were found in all experiments. Whereas previous findings for disyllables in Dutch and Spanish-languages with relatively clear syllable boundaries-showed effects of a frequency manipulation on 1st but not 2nd syllables, in our study English speakers were sensitive to the frequency of both syllables. We interpret this sensitivity as an indication that the production of English has more extensive planning scopes at the interface of phonetic encoding and articulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved).     

The syllable’s role in word naming

In a series of experiments, the masked priming paradigm with very brief prime exposures was used to investigate the role of the syllable in the production of English. Experiment 1 (word naming task) showed a syllable priming effect for English words with clear initial syllable boundaries (such as BALCONY), but no effect with ambisyllabic words targets (such as BALANCE, where the /l/ belongs to both the first and the second syllables). Experiment 2 failed to show such syllable priming effects in the lexical decision task. Experiment 3 demonstrated that for words with clear initial syllable boundaries, naming latencies were faster only when primes formed the first syllable of the target, in comparison with a neutral condition. Experiment 4 showed that the two possible initial syllables of ambisyllabic words facilitated word naming to the same extent, in comparison with the neutral condition. Finally, Experiment 5 demonstrated that the syllable priming effect obtained for CV words with clear initial syllable boundaries (such as DIVORCE) was not due to increased phonological and/or orthographic overlap. These results, showing that the syllable constitutes a unit of speech production in English, are discussed in relation to the model of phonological and phonetic encoding proposed by Levelt and Wheeldon (1994).     

The subjective estimation of relative syllable frequency

Ss are able to judge the relative frequency of occurrence in English of nonmorphemic syllables independent of phoneme frequency. The results support a theory of speech perception based on the syllable as a unit as opposed to the phoneme.     

Syllable monitoring in internally and externally generated English words

The ability of English speakers to monitor internally and externally generated words for syllables was investigated in this paper. An internal speech monitoring task required participants to silently generate a carrier word on hearing a semantically related prompt word (e.g., reveal—divulge). These productions were monitored for prespecified target strings that were either a syllable match (e.g., /dai/), a syllable mismatch (e.g., /daiv/), or unrelated (e.g., /hju:/) to the initial syllable of the word. In all three experiments the longer target sequence was monitored for faster. However, this tendency reached significance only when the longer string also matched a syllable in the carrier word. External speech versions of each experiment were run that yielded a similar influence of syllabicity but only when the syllable match string also had a closed structure. It was concluded that any influence of syllabicity found using either task reflected the properties of a shared perception-based monitoring system.     

The perception of /r/ and /l/ in syllable-initial and syllable-final position

American English liquids /r/ and /l/ have been considered intermediate between stop consonants and vowels acoustically, articulatorily, phonologically, and perceptually. Cutting (1947a) found position-dependent ear advantages for liquids in a dichotic listening task: syllable-initial liquids produced significant right ear advantages, while syllable-final liquids produced no reliable ear advantages. The present study employed identification and discrimination tasks to determine whether /r/and /l/ are perceived differently depending on syllable position when perception is tested by a different method. Fifteen subjects listened to two synthetically produced speech series—/li/ to /ri/ and /il/ to /ir/—in which stepwise variations of the third formant cued the difference in consonant identity. The results indicated that: (1) perception did not differ between syllable positions (in contrast to the dichotic listening results), (2) liquids in both syllable positions were perceived categorically, and (3) discrimination of a nonspeech control series did not account for the perception of the speech sounds.     

The Frame Constraint on Experimentally Elicited Speech Errors in Japanese

The so-called syllable position effect in speech errors has been interpreted as reflecting constraints posed by the frame structure of a given language, which is separately operating from linguistic content during speech production. The effect refers to the phenomenon that when a speech error occurs, replaced and replacing sounds tend to be in the same position within a syllable or word. Most of the evidence for the effect comes from analyses of naturally occurring speech errors in Indo-European languages, and there are few studies examining the effect in experimentally elicited speech errors and in other languages. This study examined whether experimentally elicited sound errors in Japanese exhibits the syllable position effect. In Japanese, the sub-syllabic unit known as “mora” is considered to be a basic sound unit in production. Results showed that the syllable position effect occurred in mora errors, suggesting that the frame constrains the ordering of sounds during speech production.     

A neuronal model for syllable representation

A speculative neuronal template, equivalent to canonical syllable forms and independent of segmental representations, is offered to help account for (1) the inviolate nature of phonotactic constraints in aphasic speech output, and (2) left hemisphere specialization for speech sound access and output. The model, which attempts to relate plausible neuronal systems to linguistic function, is based on cell assemblies that are thought to develop by way of genetic predisposition and ontogenetic language experience, into configurations that can represent canonical slot positions for the consonants and vowel comprising a syllable. The syllable is assumed to be the basic organizational rhythmic unit for serial concatenation of sublexical segments. A scheme for neurological differentiation of vowels and consonants is offered. Phonotactic constraints can become "hard-wired" to help create the automaticity underlying phonological sound organization. Testable predictions are offered to substantiate the claims of the model.     

The role of perceptual salience during the segmentation of connected speech

Statistical learning allows listeners to track transitional probabilities among syllable sequences and use these probabilities for subsequent speech segmentation. Recent studies have shown that other sources of information, such as rhythmic cues, can modulate the dependencies extracted via statistical computation. In this study, we explored how syllables made salient by a pitch rise affect the segmentation of trisyllabic words from an artificial speech stream by native speakers of three different languages (Spanish, English, and French). Results showed that, whereas performance of French participants did not significantly vary across stress positions (likely due to language-specific rhythmic characteristics), the segmentation performance of Spanish and English listeners was unaltered when syllables in word-initial and word-final positions were salient, but it dropped to chance level when salience was on the medial syllable. We argue that pitch rise in word-medial syllables draws attentional resources away from word boundaries, thus decreasing segmentation effectiveness.     

Perception of dynamic information for vowels in syllable onsets and offsets.

It has been demonstrated using the "silent-center" (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets, taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsets alone or syllable offsets alone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable offsets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as "front" or "back" was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

Diminutives facilitate word segmentation in natural speech: Cross-linguistic evidence

Final-syllable invariance is characteristic of diminutives (e.g., doggie), which are a pervasive feature of the child-directed speech registers of many languages. Invariance in word endings has been shown to facilitate word segmentation (Kempe, Brooks, & Gillis, 2005) in an incidental-learning paradigm in which synthesized Dutch pseudonouns were used. To broaden the cross-linguistic evidence for this invariance effect and to increase its ecological validity, adult English speakers (n=276) were exposed to naturally spoken Dutch or Russian pseudonouns presented in sentence contexts. A forced choice test was given to assess target recognition, with foils comprising unfamiliar syllable combinations in Experiments 1 and 2 and syllable combinations straddling word boundaries in Experiment 3. A control group (n=210) received the recognition test with no prior exposure to targets. Recognition performance improved with increasing final-syllable rhyme invariance, with larger increases for the experimental group. This confirms that word ending invariance is a valid segmentation cue in artificial, as well as naturalistic, speech and that diminutives may aid segmentation in a number of languages.     

Monitoring syllable boundaries during speech production

This study investigated the encoding of syllable boundary information during speech production in Dutch. Based on Levelt's model of phonological encoding, we hypothesized segments and syllable boundaries to be encoded in an incremental way. In a self-monitoring experiment, decisions about the syllable affiliation (first or second syllable) of a pre-specified consonant, which was the third phoneme in a word, were required (e.g., ka.No 'canoe' vs. kaN.sel 'pulpit'; capital letters indicate pivotal consonants, dots mark syllable boundaries). First syllable responses were faster than second syllable responses, indicating the incremental nature of segmental encoding and syllabification during speech production planning. The results of the experiment are discussed in the context of Levelt's model of phonological encoding.     

Naming pseudowords in Spanish: effects of syllable frequency

Three naming experiments were conducted to examine the role of the first and the second syllable during speech production in Spanish. Facilitative effects of syllable frequency with disyllabic words have been reported in Dutch and Spanish (Levelt & Wheeldon, 1994; Perea & Carreiras, 1998). In both cases, the syllable frequency effect was independent of-and additive to-the effect of word frequency. However, Levelt and Wheeldon (1994) found that words ending in a high-frequency syllable were named faster than words ending in a low-frequency syllable, whereas Perea and Carreiras (1998) found a facilitative effect of syllable frequency for the initial syllable. In Experiments 1-2, we manipulated the frequency of the first and the second syllable of disyllabic CV.CV pseudowords. In Experiment 3, participants named CVC disyllabic pseudowords for which only the frequency of the first syllable was manipulated. The experiments showed a facilitative effect of frequency of the first syllable. The findings are discussed in terms of the current models of speech production.     

Perception of dynamic information for vowels in syllable onsets and offsets

It has been demonstrated using the “silent-center” (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets,taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsetsalone or syllable offsetsalone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable off-sets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as “front” or “back” was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

Single word production in english: the role of subsyllabic units during phonological encoding

Five experiments investigated the role of sublexical units in English single word production. L. Ferrand, J. Segui, and G. W. Humphreys (1997) reported a priming effect that was most effective when primes and targets shared the first syllable. Experiments 1A and 1B failed to replicate this effect but Experiment 1B showed that subsyllabic units play a role in speech production. This role was further explored using a picture naming task in Experiment 2. Naming latencies were shortest when the segmental overlap between prime and target (the picture name) was largest, regardless of the syllable structure of the target. Experiments 3 and 4 replicated this segmental overlap effect with different sets of words as targets. Experiment 5 showed that the magnitude of the overlap effect increased with longer prime exposure duration. The implications of these results for theories of phonological encoding in speech production are discussed.     

Differential diagnosis between apraxia and dysarthria based on acoustic analysis

Acoustic analysis provides objective quantitative measures of speech that enable a comprehensive and accurate understanding of motor disorders and complement the traditional measures. This paper aims to distinguish between normal and pathological speech, more specifically between apraxia of speech and spastic dysarthria in native Spanish speaking patients using acoustic parameters. Participants (4 aphasic with apraxia of speech, 4 with spastic dysarthria, and 15 without speech disorders) performed three different tasks: repeating the syllable sequence [pa-ta-ka], repeating the isolated syllable [pa] and repeating the vowel sequence [i-u]. The results showed that the normative values of motor control, in general, coincide with those obtained in previous research on native English speakers. They also show that damage to motor control processes results in a decrease in the rate of alternating and sequential movements and an increase in the inter-syllabic time for both types of movements. A subset of the acoustic parameters analyzed, those that measure motor planning processes, enable differentiation between normal population and apraxic and dysarthric patients, and between the latter. The differences between the pathological groups support the distinction between motor planning and motor programming as described by van der Merwe's model of sensorimotor processing (1997).     

Syllable similarity: The effects of differences in vowels, consonants, and order

In five experiments with synthetic and natural speech syllables, a rating task we used to study the effects of differences in vowels, consonants, and segment order on judged syllable similarity. The results of Experiments I-IV support neither a purely phonemic model of speech representation, in which vowel, consonant, and order are represented independently, nor a purely syllabic model, in which the three factors are integrated. Instead, the data indicate that subjects compare representations in which adjacent vowel and consonant are independent of one another but are not independent of their positions in the syllable. Experiment V provided no support for the hypothesis that this position-sensitive coding is due to acoustic differences in formant transitions.     

Comparison of two training methods to enhance awareness of the oral cavity

This investigation assessed two training methods to heighten awareness of the oral cavity in normal adult speakers of English. A pretest-posttest design was used. 40 subjects (M age=25.6 yr., SD=8.7) who passed a speech and hearing screening were placed into two equal-sized groups. Each group received 10 hr. of training over 3 wk. The Experimental group received verbal instructions regarding how the phonemes of English are produced, including tongue height, location, and contact with other structures in the oral cavity. Subjects in the Experimental group also used a tongue blade to enhance lingual awareness. The Control group received instructions in articulatory placement only. The Lingual Awareness Test required subjects to imitate 7 English syllables and answer 4 multiple-choice questions regarding lingual contact for each syllable. Posttest scores for the Experimental group were significantly better for one phoneme. The Control group made no significant improvement.     

Hemispheric specialization for the perception of speech sounds: The influence of intonation and structure

The present report investigates the effect of various cues to phrase structure upon the hemispherically lateralized processing of phonetic structure. Meaningless sequences were paired for dichotic presentation and were delivered under two different conditions termed structured and semistructured. The dichotic sequences in the two conditions contained the same nonsense syllable stems, English bound morphemes, and English function words. Also each of the sequences in both conditions were grammatically ordered in the sense that if the nonsense stems were replaced by English stems, a grammatical sentence would result. The conditions differed with respect to prosody, however: the structured sequences were characterized by the acoustic correlates of constituent structure; the semistructured sequences were delivered in a monotone. A significant right-ear superiority was observed in the structured condition, but not in the semistructured condition. These perceptual laterality differences are discussed in relation to cerebral dominance for language and in relation to speech processing generally.     

Syllable frequency and syllable structure in apraxia of speech

Recent accounts of the pathomechanism underlying apraxia of speech (AOS) were based on the speech production model of Levelt, Roelofs, and Meyer, and Meyer (1999)1999. The apraxic impairment was localized to the phonetic encoding level where the model postulates a mental store of motor programs for high-frequency syllables. Varley and Whiteside (2001a) assumed that in patients with AOS syllabic motor programs are no longer accessible and that these patients are required to use a subsyllabic encoding route. In this study, we tested this hypothesis by exploring the influence of syllable frequency and syllable structure on word repetition in 10 patients with AOS. A significant effect of syllable frequency on error rates was found. Moreover, apraxic errors on consonant clusters were influenced by their position relative to syllable boundaries. These results demonstrate that apraxic patients have access to the syllabary, but that they fail to retrieve the syllabic motor patterns correctly. Our findings are incompatible with a subsyllabic route model of apraxia of speech.