The linguistic nature of developmental Dyslexia: an electrophysiological and behavioural investigation

The present thesis faces the ongoing debate on the linguistic nature of Developmental Dyslexia (DD), based on evidence of grammatical deficits in dyslexic individuals (e.g., Robertson & Joanisse, 2010), and on the frequently reported overlap with Specific Language Impairment (e.g., Bishop & Snowling, 2004). In particular, the morphosyntactic processing deficit in DD has been explored by means of particularly sensitive measures, namely event-related potentials (ERPs). The dissertation collects the results from three studies performed on different samples of individuals with DD (Italian adults, Italian children, and German adults), reporting consistent data in support of a general morphosyntactic processing weakness. Specifically, the ERP results reveal different language processing modalities in the dyslexic samples, characterised by the need of an additional process related to rules retrieval and/or lexical access. Further behavioural data collected on the same participants support the ERP data. In the third study, advantage has been taken of the morphological features characterising German to additionally investigate the specificity of the reported morphosyntactic deficits, and their relationship with phonological and acoustical processing difficulties. The results are discussed within a developmental and psycholinguistic framework.