From our Community:
Can Dyslexia and Dysgraphia Affect IQ Scores?
My son got officially diagnosed with both dyslexia and dysgraphia this week. I suspected he would come back with the diagnosis. What surprised me a bit were his IQ scores.
The scenario is a common one – one sibling is dyslexic while the other is not. The non-dyslexic student qualifies easily for a highly capable / gifted program while the dyslexic one does not…although that may be the one who is a “head turner” because of creative thinking, intuitive leaps, and general reasoning and questioning capacity.
The short answer is YES. There are many individual factors that can affect the accuracy of a student’s testing. A student’s temperament (perfectionistic, introverted), oral fluency, persistence / resilience, verbal precision, and many more factors can affect whether scores reflect intellectual ability.
However, in regard to IQ tests, there are also potential pros and cons depending on which tests were chosen (e.g. WISC-V vs. WJIV). We prefer the WISCV-WIAT combination because the WIAT is a more comprehensive way to assess difficulties with writing at the essay level as well a components like sentence combining and formulation. Some professionals avoid the WIAT because it is much longer to administer and requires more subjective analysis regarding the scoring of an essay and its organization. We think it especially important to include (if possible) though because for many older dyslexics, the written essay is major challenge to them succeeding in higher education.
It is always important to have a professional check a General Ability Index if a student is gifted and dyslexic – because a full scale IQ score alone would not be representative of advanced conceptual and reasoning ability. The GAI can be considered to a Full Scale IQ equivalent when there is a significant amount of score discrepancies due to dyslexia. In the WISC-V, the 4 scores that comprise the GAI are 2 Verbal reasoning scores (Similarities and Vocabulary), 3 Nonverbal scores (Block design, Matrix reasoning, and Figure weights). Importantly lower scores in Symbol search, Coding (copying written symbols), or Digit span (auditory working memory and sequencing) aren’t factored into the GAI…an important requirement if the full scale IQ equivalent is to be an accurate estimate of a student’s reasoning and conceptual ability and fund of knowledge. Both Dyslexia and Dysgraphia are associated with lower scores in Coding, Symbol Search, and Digit Span.
Probably the most typical profile for a gifted dyslexic student in our clinic is to have the highest values in verbal reasoning, followed by non-verbal reasoning. Working memory is weaker (compared to age peers) when younger, but tends to settle in the average range. By far the lowest scores that we see are processing speed – and this usually means a student also has dysgraphia.
We include some of the technical comparisons below for some of our professional members, but be aware that some psychologists are wary that discrepancies between the WISC and WIAT are higher in the general population than discrepancies between the Woodcock Johnson Ability and Achievement test. Much of that complaint is centered are small differences, however and in our practice we state consensus thresholds to be > 20-25 points discrepancy as indicative of moderate to severe “Specific Learning Disability” or dyslexia, dysgraphia, or dyscalculia, depending on the subtests in question.
It is important for parents to be aware of the artificial lowering of IQ scores for their students because if the GAI makes the cut-off for gifted programs, an optimal placement may be in gifted classes with appropriate accommodations.