In: Learning and Memory Developments… Editor: Lucas C. Eklund and Aron S. Nyman
ISBN: 978-1-60876-397-9 © 2009 Nova Science Publishers, Inc.
Chapter 6
INTELLECTUAL DISABILITY: BEYOND IQ SCORES Nahal Goharpey2, David P. Crewther2 and Sheila G. Crewther1* 1
School of Psychological Science, La Trobe University, Victoria, Australia, 3086. 2 Brain Sciences Institute, Swinburne University of Technology, Hawthorn, Australia, 3122.
ABSTRACT Currently Intellectual disability (ID) is classified as a Wechsler Intelligence Scale for Children- Fourth Edition (WISC-IV) Intelligence Quotient (IQ) below 70 and an impairment in adaptive skills during the developmental period. We argue that because so many children/adults with ID have language based deficits, mental age comparison or matching of individuals from different ID groups or to a typically developing (TD) group should be according to their overall performance on a non-verbally based measure, such as the Raven’s Coloured Progressive Matrices (RCPM). We suggest that the RCPM should replace the commonly used WISC-IV measure of intelligence, as a means of matching groups of ID and TD group on mental age as it is a better measure of reasoning ability in children with ID who invariably have verbally based deficits. In addition, we present evidence that RCPM mental aged matched children with low functioning Autism Spectrum Disorder (ASD), Down Syndrome (DS), idiopathic ID use different problem solving strategies than TD children, to achieve the same overall performance on the RCPM. This is presumably due to group difference in brain impairments as evidenced by brain imaging studies. We also present evidence from the literature that working memory is a major component of successful performance on an IQ test and impairment in working memory in ID could also affect problem solving abilities on the RCPM. The theoretical and educational implications of the discrepancy between similar overall performance level on an intelligence test, but different use of strategy are also explored.
*
Corresponding author: 400 Burwood Rd., Bundoora, Victoria , Australia 3086,
[email protected], t +613 9214 5877, f +6139214 5525
2
Nahal Goharpey, David P. Crewther and Sheila G. Crewther
Keywords: Intellectual Disability, Autism Spectrum Disorder, Down Syndrome, Idiopathic Intellectual Disability, working memory, Ravens coloured progressive matrices, WISC-IV.
Intellectual disability (ID) is commonly defined by three criteria: (1) a Wechsler Intelligence Sale for Children intelligence quotient (IQ) 2 SD below the norm of 100 (i.e.
