Cognitive Abilities and Literacy: The Role of Intelligence in Reading Skills

The present study aims to explore the relationship between cognitive abilities and reading skills in children and adolescents. Significant correlations have been found between the cognitive domains working memory, verbal comprehension, processing speed, and perceptual reasoning and specific reading skills, such as reading speed, fluency, and reading comprehension. Current research emphasizes the impact of biological explanations of reading difficulties as well as phonological processing. Both are closely related to cognitive performance. A low IQ score is mandatory for the diagnosis of developmental dyslexia in a clinical context. The present study analyzes the impact of IQ performance on reading and whether the current recommendations of diagnostic criteria for reading difficulties in Germany are applicable. A sample of 101 German children ranging in age from 7 to 16 years were compared regarding their IQ scores and their reading skills. Cognitive performance was assessed with the Wechsler Intelligence Scale for Children - 4th Edition (WISC-IV; Petermann & Petermann, 2011). Reading skills were measured using two standardized reading tests (Zrcher Lesetest-II [Petermann& Daseking, 2012], Ein Leseverstandnistest fur Erst- bis Sechstklassler [Lenhard & Schneider, 2006]). Correlations and multiple hierarchical regression analyses were carried out in order to quantify the impact of cognitive and other variables (gender, speech development) on reading skills. Cognitive performance and reading are correlated. Working memory has the highest impact on reading skills (r = .51-.60) followed by verbal comprehension (r = .40-.50). Our findings correspond to those of other studies focusing on similar aspects of reading. The percentage of variance explained by the regression analyses is moderate (R-2 = .50). Working memory and its different aspects are closely related to processes underlying reading skills. If the acquisition of symbol coding is disturbed because of poor memory, fluent reading will not be possible. Working memory aspects include the visuospatial sketchbook, which is also part of processing speed. Along with visual perception and verbal comprehension, these cognitive skills form the basic prerequisites for learning to read. The importance of cognitive abilities for academic achievement has been acknowledged in the diagnostic criteria for dyslexia: According to ICD-10, developmental dyslexia is marked by reading achievement that falls substantially below that expected given the individual's chronological age, measured intelligence, and age-appropriate education. The determination of the discrepancy, however, is not a fixed factor: the latest guidelines of the German Society of Child and Adolescent Psychiatry, Psychosomatics, and Psychotherapy (DGKJP) recommend the use of the IQ discrepancy as one option among others, with the German Society of Psychology (DGPs) even suggesting the rejection of the IQ discrepancy. Considering our results, we support the application of the regression model, which has been established to allow for dyslexia diagnoses even for children with high IQ scores. It integrates the correlation of cognitive performance and reading skills and provides specific cut-off scores for reading test results.