title: IQ of four-year-olds who go on to develop dyslexia.
abstract: Do children who go on to develop dyslexia show normal verbal and nonverbal development before reading onset? According to the aptitude-achievement discrepancy model, dyslexia is defined as a discrepancy between intelligence and reading achievement. One of the underlying assumptions is that the general cognitive development of children who fail to learn to read has been normal. The current study tests this assumption. In addition, we investigated whether possible IQ deficits are uniquely related to later reading or are also related to arithmetic. Four-year-olds (N = 212) with and without familial risk for dyslexia were assessed on 10 IQ subtests. Reading and arithmetic skills were measured 4 years later, at the end of Grade 2. Relative to the controls, the at-risk group without dyslexia had subtle impairments only in the verbal domain, whereas the at-risk group with dyslexia lagged behind across IQ tasks. Nonverbal IQ was associated with both reading and arithmetic, whereas verbal IQ was uniquely related to later reading. The children who went on to develop dyslexia performed relatively poorly in both verbal and nonverbal abilities at age 4, which challenges the discrepancy model. Furthermore, we discuss possible causal and epiphenomenal models explaining the links between early IQ and later reading.
authors.affiliation: University of Amsterdam, Amsterdam, Netherlands University of Oxford, Oxford, UK elsje.vanbergen@psy.ox.ac.uk.
authors.forename: Elsje
authors.initials: E
authors.lastname: van Bergen
authors.affiliation: University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Peter F
authors.initials: PF
authors.lastname: de Jong
authors.affiliation: University of Groningen, Groningen, Netherlands.
authors.forename: Ben
authors.initials: B
authors.lastname: Maassen
authors.affiliation: Radboud University Nijmegen, Nijmegen, Netherlands.
authors.forename: Evelien
authors.initials: E
authors.lastname: Krikhaar
authors.affiliation: University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Anna
authors.initials: A
authors.lastname: Plakas
authors.affiliation: University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Aryan
authors.initials: A
authors.lastname: van der Leij
mesh_terms: D000124:Achievement; D001077:Aptitude Tests; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D060705:Dyscalculia / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D004410:Dyslexia / Q000175:diagnosis* / Q000235:genetics / Q000523:psychology*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007360:Intelligence; D008297:Male; D009426:Netherlands; D010700:Phonetics; D011932:Reading; D018570:Risk Assessment; D012660:Semantics; D014706:Verbal Learning
keywords: IQ; arithmetic; dyslexia; familial risk; reading