The conscious awareness and underlying representation of syllabic stress in skilled adult readers and adults with developmental dyslexia

The relationship between phonemic awareness and literacy ability is well established in the developmental and adult reading literatures. Recent research indicates that awareness of the rhythmic patterns present in spoken language (i.e. prosody) may also be an important predictor of reading ability. Researchers have demonstrated that sensitivity to speech prosody can facilitate speech segmentation and the development of phoneme awareness. Awareness of the rhythmic patterns in spoken words and phrases is also known to play a direct role in phonological decoding, reading comprehension and learning to use punctuation. These findings have the potential to enhance our understanding of typical reading development and inform theories of how poor phonological and auditory skills contribute to dyslexia. This research also helps extend our knowledge of skilled and impaired reading to a wider range of reading materials (e.g. multisyllabic words) and thus raises issues relevant to cognitive models of visual word recognition. A small number of studies have demonstrated that sensitivity to the prosodic patterns in spoken language is reduced in children with dyslexia. However, there is currently no published research investigating the prosodic processing skills of adults with dyslexia. The precise nature of the prosodic processing deficit associated with dyslexia is also unclear. These gaps in the literature are problematic because phonological processing is multifaceted and the relationship between specific phonological skills and reading ability may change over time. This thesis presents four cross sectional studies in which adults with dyslexia were compared with control participants matched for age and IQ on various tasks designed to measure prosodic processing. The experiments also contrast the conscious awareness of prosodic structure with the underlying representation of syllabic stress assignment in the mental lexicon and the ability to acquire spelling-sound correspondences for decoding stress assignment in multisyllabic words. Participants with dyslexia showed reduced awareness of lexical and metrical prosody and these skills were found to be significantly associated with, and predictive of, phoneme awareness and phonological decoding ability (Experiments 1a and 2). In contrast, adults with dyslexia showed normal patterns of stress based priming at magnitudes similar to controls (Experiments 1b and 2). Similar, although somewhat weaker results were also obtained when lexical stress was primed with abstract stress templates rather than real-word stimuli (Experiment 3). Participants with dyslexia also showed normal effects of spelling-stress congruency on lexical decision times for disyllabic words (Experiment 4). The overall pattern of results strongly suggests that the prosodic processing problems associated with dyslexia in adulthood are limited to tasks requiring participants to access and consciously reflect upon their knowledge of prosodic structure, or to process information related to prosodic structure in an abstract way. In contrast, the ability of adults with dyslexia to represent lexical stress assignment in the mental lexicon, assemble novel prosodic representations, and learn correspondences between lexical stress assignment and aspects of orthographic structure appears to be intact. Encouragingly, this pattern of results is consistent with recent findings reported in the domain of phonemic processing