Dyslexia affects a large portion of the population, and identification of the individuals affected is important for effective intervention/accommodation that will facilitate the best outcomes. Screening is an important first step in the identification of individual s with the disorder. The measures utilized for this purpose must be effective, in order to ensure maximum accuracy, so that individuals are correctly identified, and are able to access the assistance required to mitigate the effects of the disorder. Currently, there are only a few tests available to screen for dyslexia in adults, and research evidence of their effectiveness is limited. This thesis provides: (1) in Chapter 2, a limited review of
currently available screening tools; (2) in Chapters 3 and 6, empirical studies of the psychometric properties of two dyslexia screening tests for adults currently in use in the United Kingdom, the Bangor Dyslexia Test (BDT) and the Instines; (3) in Chapters 4 and 5, empirical studies of the development of a new test, the Bangor Adult Literacy Index (BALI); and (4) in Chapter 7, a study of
the predictors (including several component measures of the BALI) of literacy skills among adults with and without dyslexia. The main findings across the research programme reported in this thesis are as follows. The review of the screening tools (Chapter 2) highlighted a lack of independent research studies on the tests and little empirical evidence to support the validity and reliability of
some of the tests. The results of the evaluation of the BDT (Chapter 3) revealed that it is psychometrically sound and effectively discriminates
between adults with and without dyslexia. For the Instines (Chapter 6), the opposite was true, and the validity and reliability of the test was found to be questionable. For the new screening measure, the BALI (Chapters 4 and 5)
, the results provided evidence of the validity and reliability of the tasks selected for inclusion. This new tool proved to be an excellent discriminator of dyslexic and non-dyslexic adult groups. The results of the investigation of the
profiles of cognitive predictors of literacy skills for adults with and without
dyslexia (Chapter 7) provided evidence that the predictors are similar to those identified for children. Importantly, we also found evidence to suggest that the profiles of cognitive predictors of literacy skills, and the effects of IQ on these in adults with dyslexia, are the same or similar regardless of IQ level. Together, these studies have contributed to research into dyslexia in adulthood by
enhancing the literature available on dyslexia screening tests and our understanding of the manifestation of dyslexia in this population.