The visual attention span as a measure of orthographic grain size: effects of orthograpic depth and morphological complexity.
This thesis studies some of the factors modulating the size of the orthographic units (or grains) that are used in reading. Two of these factors are reading expertise and word familiarity that are both related to whether the individual can link the orthographic units of the word to its orthographic and subsequently phonological and semantic representations in the lexicon. The thesis studies how this skill develops and the possible influence of the mappings between lexical and sub-lexical orthographic grains at the semantic/morphological and phonological level by studying the influence of orthographic depth and morphological complexity. The main goal of this thesis was to specifically study the modulation of orthographic grain size in reading, focusing on the visual aspects of orthographic processing and using the visual attention span as an indirect measure of orthographic grain size in reading. In particular, we studied the effect of a language's orthographic depth and morphological characteristics on orthographic grain size with two cross-linguistic studies (in readers of Basque, Spanish and French), and the effect of morphological structure at the word level (morphological complexity) on orthographic grain size with two studies in Basque. Our results provided support for the modulation of orthographic grain size based on orthographic depth, language morphology and morphological complexity, and for the adequacy of the visual attention span as a measure of orthographic grain size. Overall, the present thesis suggests a new perspective through which to study the visual demands and limitations imposed on orthographic processing during reading development in alphabetic orthographies.