Dyslexia among adults : Neuropsychology and personality

Abstract: Reading and writing skills are of crucial importance in modern society. Therefore, dyslexia is a significant handicap, not only in respect of lexical skills and processing of language-based information - it appears to have social consequences as well, as evidenced for instance by the high frequency of dyslexics among long-term unemployed people. One major research problem is that the term dyslexia is not well-defined. In consequence, there is no consensus about epidemiology, causal factors and correlates. However, some findings tend to be reported more consistently among dyslexics; phonological deficits, a relatively unresponsive visual magnocellular system and problems with automatization of complex cognitive tasks. Furthermore, impaired memory functioning and low self-esteem are associated with dyslexia. Another research problem is that our knowledge of dyslexia is to a large extent based on studies of children. Lacking direct evidence from studies of adults, we tend to extrapolate our knowledge about children. The aim of the present thesis, which comprises five empirical studies, was to explore neuropsychological and personality correlates of dyslexia among adults. We found a high frequency of dyslexics among prison inmates (41%), who performed more poorly on most of the neuropsychological tasks, and had a deviant personality pattern: higher anxiety and more deviant scores on scales reflecting social interactions, compared to non-dyslexic inmates. Non-criminal dyslexics used an inflexible strategy in a continuous performance test, an attribute that also characterized prison inmates, dyslexic or not. Dyslexics were less prone, or able, to shift from an egocentric perspective when invited to view a statement from another's psychological perspective, compared to non-dyslexics. Furthermore, these dyslexics had more difficulties to understand certain concepts reflecting emotional states and social interactions. Some aspects of the deviant personality pattern described in dyslexics, and corroborated by our own previous findings, were demonstrated to reflect ADHD rather than dyslexia. In contrast, memory dysfunction appears to be a stable correlate of dyslexia. Finally, we evaluated a 20 week educational programme for dyslexics. Reading and writing skills, memory and self-confidence improved compared to dyslexic controls. The findings are discussed in a neo-Darwinian context, favouring the theory that the evolution of language is based on pre-language mental faculties serving skills needed for complex social interactions, rather than a new and specific "language" faculty. Problems and consequences of the lack of consensus about the definition of dyslexia are also discussed, concluding that these differences are of minor importance when we design remediation interventions.