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.

Sensitivity to amplitude envelope rise time in infancy and vocabulary development at 3 years: A significant relationship

“…As predicted, scores for the FR group were consistently lower for these verbal tasks; however, the group differences were not significant. Non‐verbal IQ was significantly lower for the FR than the CTR group, but the FR group's scores were within age norms, a pattern consistent with previous research with children at‐risk for dyslexia (van Bergen et al, ).…”

Preliteracy signatures of poor-reading abilities in resting-state EEG

“…Our behavioral results confirm this effect in poor readers showing that at-risk non-fluent children scored lower than both at-risk fluent and control children in all reading-related tests (Phonological Awareness, Orthographical Knowledge and RAN). Our data on intelligence measures were in agreement with previous findings showing that dyslexics score slightly lower on verbal tasks despite having adequate reasoning abilities compared to non-impaired readers (Snowling et al, 2003; van Bergen et al, 2013). …”

“…This is a well-known effect and poor verbal abilities have been reported to be present already at preliteracy age in children later diagnosed with dyslexia studies (Snowling et al, 2003; van Bergen et al, 2013). …”

Pathways Into Literacy: The Role of Early Oral Language Abilities and Family Risk for Dyslexia

“…Norm-based standard scores ( M = 100, SD = 15) for each subtest were used for the analyses. A more elaborate description of the verbal and nonverbal intelligence tests and the details of the individual subtests are provided by van Bergen, de Jong, Maassen, Krikhaar, et al (2014) . Reliabilities of the subtests were .90, .90, .86, and .79, respectively.…”