Socioeconomic status, age and the classification of dyslexics and poor readers: the dangers of using IQ scores in the definition of reading disability

Abstract

Two studies are reported that raise additional serious questions about the use of IQ scores in the definition of dyslexia. Participants in the studies were children with reading difficulties and IQ _80. Children were categorized into 'dyslexic' and 'poor reader' groups on the basis of whether or not there was a significant discrepancy between their IQ and their reading performance. The first study was based on a sample of 161 7-8-year-old children. There was a significant positive correlation (0.351) between the IQ scores of the children and the socioeconomic status (SES) scores of the parents. Furthermore, the dyslexic children had significantly higher SES scores than the poor readers. The second study investigated the changes in IQ with age, using a total of 473 children aged 7-16 years. Two key findings emerged: first, the mean IQ scores were lower for the older children, suggesting an effective decline with age; second, the ratio of poor readers to dyslexic children increased with age. The findings suggest strongly that the measured IQ of a dyslexic child decreases with age, leading to a reclassification from dyslexic to poor reader using the discrepancy approach. Two children with equivalent reading difficulties might therefore be diagnosed differently by the IQ-attainment discrepancy criterion, with a child with lower SES or who is older being more likely to be classified as a poor reader. Therefore children with lower SES or who are older are victims of discrimination if the IQ-achievement discrepancy definition of dyslexia is used.

Reading and writing disabilities among inmates in correctional settings. A Swedish perspective

“…it will prevent confounding factors such as including "a garden variety of poor readers". However, many studies have shown that poor readers present the same problem with decoding and spelling irrespective of IQ level (Fletcher et al, 1994;Gustafson & Samuelsson, 1999;Siegel & Himel, 1998;Stanovich & Siegel, 1994;Vellutino, Scanlon, & Lyon, 2000). Thus, in contrast to the view that the IQ discrepancy definition discerns a more "plain" group of dyslexics, the truth might actually be the opposite.…”

Detecting Different Types of Reading Difficulties: A Comparison of Tests

“…Consistent with previous research (Siegel, 1992;Siegel & Himel, 1998;Tanaka et al, 2011), nonverbal IQ was not associated with performance on any of the reading measures. These findings provide further evidence to suggest that reading difficulties and dyslexia should not be defined by reference to a child's IQ level.…”

Gender ratio and cognitive profiles in dyslexia: a cross-national study

“…However, a discrepancy between reading achievement and IQ was not included in our definition of dyslexia. There is empirical evidence that traditional IQ-based discrepancy formula may introduce a gender bias such that boys with a RD are more likely to be identified than girls with RD (Share & Silva, 2003;Siegel & Himel, 1998;Siegel & Smythe, 2005). Normally achieving readers were identified through the following criteria: (a) reading comprehension equal or above the 50th percentile; (b) a percentile score above 25 on accuracy on pseudoword reading from naming task of the Sicole-R; (c) a percentile below 75 on reading time on pseudoword or word reading from naming task of the Sicole-R; and (d) an IQ [ 75.…”