The role of word morphology in typical and atypical reading acquisition: a comparison between altered and pseudoalterate nouns.

Several studies have shown the role of morphological structure when processing complex words. However, the debate is still open for what concerns the processing level (orthographical, lexical, or semantic) that is involved in morphological parsing. In Italian, hints on this issue may derive from the use of alterate nouns (e.g. gattino, little cat), due to the high productivity, regularity and transparency of the evaluative suffixes. Thirty-two children with dyslexia and 64 same-age skilled readers (mean age: 134 months) were asked to read transparent alterate nouns (e.g. librone, libr+one, big book), fully parsable pseudo-alterate nouns (e.g. mattone, brick, but pseudo-derived from matto, crazy man) and simple nouns ending with a pseudo-suffix (e.g. carbone, coal, where carbo is a nonword). Data were analysed for reaction times, accuracy and type of errors. Alterate nouns were read faster and more accurately than simple words, while no difference emerged between the two types of pseudoaffixed simple words. The error analysis indicates a relative sparing of the word boundaries, i.e. that errors usually involved either the root or the evaluative suffix. Data suggest that children with dyslexia take advantage from the possibility to detect a real root in the stimulus word, while typically developing children take advantage of the root as well as of the whole word, and read alterate nouns faster and more accurately than pseudoalterate nouns. Furthermore, the qualitative analysis allowed us to distribute children with dyslexia by subtypes of reading deficits. Data are in favour of a dual-route access to morphologically complex words based on both whole words and their morphemic constituents, linked to semantic representations.