The effect of talker and intonation variability on speech perception in noise in children with dyslexia.

PURPOSE: In this study, the authors aimed to determine whether children with dyslexia (hereafter referred to as "DYS children") are more affected than children with average reading ability (hereafter referred to as "AR children") by talker and intonation variability when perceiving speech in noise. METHOD: Thirty-four DYS and 25 AR children were tested on their perception of consonants in naturally produced CV tokens in multitalker babble. Twelve CVs were presented for identification in four conditions varying in the degree of talker and intonation variability. Consonant place (/bi/-/di/) and voicing (/bi/-/pi/) discrimination were investigated with the same conditions. RESULTS: DYS children made slightly more identification errors than AR children but only for conditions with variable intonation. Errors were more frequent for a subset of consonants, generally weakly encoded for AR children, for tokens with intonation patterns (steady and rise-fall) that occur infrequently in connected discourse. In discrimination tasks, which have a greater memory and cognitive load, DYS children scored lower than AR children across all conditions. CONCLUSIONS: Unusual intonation patterns had a disproportionate (but small) effect on consonant intelligibility in noise for DYS children, but adding talker variability did not. DYS children do not appear to have a general problem in perceiving speech in degraded conditions, which makes it unlikely that they lack robust phonological representations.

Investigating speech perception in children with dyslexia: is there evidence of a consistent deficit in individuals?

PURPOSE: The claim that speech perception abilities are impaired in dyslexia was investigated in a group of 62 children with dyslexia and 51 average readers matched in age. METHOD: To test whether there was robust evidence of speech perception deficits in children with dyslexia, speech perception in noise and quiet was measured using 8 different tasks involving the identification and discrimination of a complex and highly natural synthetic "bee"-"pea" contrast (copy synthesized from natural models) and the perception of naturally produced words. RESULTS: Children with dyslexia, on average, performed more poorly than did average readers in the synthetic syllables identification task in quiet and in across-category discrimination (but not when tested using an adaptive procedure). They did not differ from average readers on 2 tasks of word recognition in noise or identification of synthetic syllables in noise. For all tasks, a majority of individual children with dyslexia performed within norms. Finally, speech perception generally did not correlate with pseudoword reading or phonological processing--the core skills related to dyslexia. CONCLUSIONS: On the tasks and speech stimuli that the authors used, most children with dyslexia did not appear to show a consistent deficit in speech perception.

Developmental disorders of language and literacy: special issue.

Language and literacy are cognitive skills of exceptional complexity. It is therefore not surprising that they are at risk of impairment either during development or as a result of damage (e.g. stroke) later in life. Impaired language and literacy can arise from a general learning impairment. However, two developmental disorders, specific language impairment (SLI) and dyslexia, which affect oral and written language, respectively, are 'specific' in that they are not part of a more general learning difficulty. SLI and dyslexia each affect 5-10% of the general population, and they are the focus of the papers in this special issue.

Speech perception abilities of adults with dyslexia: is there any evidence for a true deficit?

PURPOSE: This study investigated whether adults with dyslexia show evidence of a consistent speech perception deficit by testing phoneme categorization and word perception in noise. METHOD: Seventeen adults with dyslexia and 20 average readers underwent a test battery including standardized reading, language and phonological awareness tests, and tests of speech perception. Categorization of a pea/bee voicing contrast was evaluated using adaptive identification and discrimination tasks, presented in quiet and in noise, and a fixed-step discrimination task. Two further tests of word perception in noise were presented. RESULTS: There were no significant group differences for categorization in quiet or noise, across- and within-category discrimination as measured adaptively, or word perception, but average readers showed better across- and within-category discrimination in the fixed-step discrimination task. Individuals did not show consistent poor performance across related tasks. CONCLUSIONS: The small number of group differences, and lack of consistent poor individual performance, suggests weak support for a speech perception deficit in dyslexia. It seems likely that at least some poor performances are attributable to nonsensory factors like attention. It may also be that some individuals with dyslexia have speech perceptual acuity that is at the lower end of the normal range and exacerbated by nonsensory factors.