Do dyslexia and stuttering share a processing deficit?

This study assessed the prevalence of childhood stuttering in adults with dyslexia (AWD) and the prevalence of dyslexia in adults who stutter (AWS). In addition, the linguistic profiles of 50 AWD, 30 AWS and 84 neurotypical adults were measured. We found that 17 out of 50 AWD (34 %) reported stuttering during childhood compared to 1 % of the neurotypical population. This was moderated by the severity of dyslexia: People with mild dyslexia showed a lower prevalence rate (15 %) of childhood stuttering than those with severe dyslexia (47 %). In addition, we observed that 50 % of the AWS (n = 30) fulfilled the diagnostic criteria of dyslexia, even though they had never been diagnosed as dyslexic. Compared to neurotypical adults, phonological working memory, awareness, and retrieval were similarly reduced in AWS and AWD. The findings supports the view that stuttering and dyslexia may share a phonological deficit.

The relationship between language production and verbal short-term memory: the role of stress grouping.

This study investigates the influence of stress grouping on verbal short-term memory (STM). English speakers show a preference to combine syllables into trochaic groups, both lexically and in continuous speech. In two serial recall experiments, auditory lists of nonsense syllables were presented with either trochaic (STRONG-weak) or iambic (weak-STRONG) stress patterns, or in monotone. The acoustic correlates that carry stress were also manipulated in order to examine the relationship between input and output processes during recall. In Experiment 1, stressed and unstressed syllables differed in intensity and pitch but were matched for spoken duration. Significantly more syllables were recalled in the trochaic stress pattern condition than in the iambic and monotone conditions, which did not differ. In Experiment 2, spoken duration and pitch were manipulated but intensity was held constant. No effects of stress grouping were observed, suggesting that intensity is a critical acoustic factor for trochaic grouping. Acoustic analyses demonstrated that speech output was not identical to the auditory input, but that participants generated correct stress patterns by manipulating acoustic correlates in the same way in both experiments. These data challenge the idea of a language-independent STM store and support the notion of separable phonological input and output processes.

Repeating words in sentences: effects of sentence structure.

An online picture description methodology was used to investigate the interaction between lexical and syntactic information in spoken sentence production. In response to arrays of moving pictures, participants generated prepositional sentences, such as "The apple moves towards the dog," as well as coordinate noun phrase sentences, such as "The apple and the dog move up." In Experiments 1 and 2, speakers produced the same sentence structures on prime and target trials. In addition, a pictured object was repeated in either similar or different sentence positions. Lexical repetition speeded sentence production when it occurred on the first item of the target sentence (Experiments 1 and 2). However, priming was dependent on the structural position of the to-be-repeated word in the prime sentence. In particular, a noun that occurred in a prepositional phrase did not result in facilitation when it was repeated as the head of the subject phrase (Experiment 1). This effect was shown to be independent of differences in the linear position of the repeated word in prime and target trials (Experiments 2). Experiments 3 and 4 demonstrated that lexical repetition returns when the effect of sentence structure is removed. Possible mechanisms for this interaction between lexical and structural repetition are explored.

Planning scope in spoken sentence production: the role of grammatical units.

Four experiments investigate the scope of grammatical planning during spoken sentence production in Japanese and English. Experiment 1 shows that sentence latencies vary with length of sentence-initial subject phrase. Exploiting the head-final property of Japanese, Experiments 2 and 3 extend this result by showing that in a 2-phrase subject phrase, sentence latency varies with the length of the sentence-initial phrase rather than that of the whole subject phrase or its head phrase. Experiment 4 confirms this finding in English. The authors' interpretation suggests that these effects derive from grammatical encoding processes. Planning scope varies according to the relation between the 2 phrases composing the subject phrase. A thematically defined functional phrase is suggested as defining this scope.

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 minimal unit of phonological encoding: prosodic or lexical word.

Wheeldon and Lahiri (Journal of Memory and Language 37 (1997) 356) used a prepared speech production task (Sternberg, S., Monsell, S., Knoll, R. L., & Wright, C. E. (1978). The latency and duration of rapid movement sequences: comparisons of speech and typewriting. In G. E. Stelmach (Ed.), Information processing in motor control and learning (pp. 117-152). New York: Academic Press; Sternberg, S., Wright, C. E., Knoll, R. L., & Monsell, S. (1980). Motor programs in rapid speech: additional evidence. In R. A. Cole (Ed.), The perception and production of fluent speech (pp. 507-534). Hillsdale, NJ: Erlbaum) to demonstrate that the latency to articulate a sentence is a function of the number of phonological words it comprises. Latencies for the sentence [Ik zoek het] [water] 'I seek the water' were shorter than latencies for sentences like [Ik zoek] [vers] [water] 'I seek fresh water'. We extend this research by examining the prepared production of utterances containing phonological words that are less than a lexical word in length. Dutch compounds (e.g. ooglid 'eyelid') form a single morphosyntactic word and a phonological word, which in turn includes two phonological words. We compare their prepared production latencies to those syntactic phrases consisting of an adjective and a noun (e.g. oud lid 'old member') which comprise two morphosyntactic and two phonological words, and to morphologically simple words (e.g. orgel 'organ') which comprise one morphosyntactic and one phonological word. Our findings demonstrate that the effect is limited to phrasal level phonological words, suggesting that production models need to make a distinction between lexical and phrasal phonology.