title: Lexicality and stimulus length effects in Italian dyslexics: role of the overadditivity effect.
abstract: The effect of lexicality and stimulus length was studied in 32 third- and fourth-grade Italian dyslexics and in 86 age-matched controls. A visual lexical decision task was used. As proposed by Faust et al. (1999), the results were analyzed in terms of raw reaction time (RT) data and using the z-score transformation to control for the presence of overadditivity effects. In terms of RTs, dyslexics showed a larger difference between words and nonwords (lexicality effect) and between short and long stimuli (length effect) than proficient readers. When data were transformed into z scores, only the group by length interaction remained significant while that with lexicality vanished. This pattern indicates that stimulus length has a specific role in Italian dyslexics' reading deficit; in contrast, slowness in responding to nonwords was not specific but was interpreted as one aspect of dyslexics' general inability to deal with alphabetical material (overadditivity effect).
authors.affiliation: Neuropsychology Unit, IRCCS Fondazione Santa Lucia, Roma. gloria.difilippo@uniroma1.it
authors.forename: Gloria
authors.initials: G
authors.lastname: Di Filippo
authors.forename: Maria
authors.initials: M
authors.lastname: de Luca
authors.forename: Anna
authors.initials: A
authors.lastname: Judica
authors.forename: Donatella
authors.initials: D
authors.lastname: Spinelli
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Zoccolotti
mesh_terms: D000328:Adult; D004410:Dyslexia / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007558:Italy; D007802:Language; D008297:Male; D011930:Reaction Time; D014825:Vocabulary