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Processing Speed and General Ability Index (GAI)

By Inderbir Kaur Sandhu, Ph.D

Q: I am wondering how much of an impact/effect will a Processing speed SS of 68 on the WISC IV have on a child who has General Ability Index of 103. He has met criteria for Specific Learning Disability in Math Calc. and demonstrates specific and significant processing weakness across measures of working memory, sustained attention and impulse control, organization and planning, and abstract learning and memory. Therefore, the presence of executive functioning deficit has also been identified.

Also, how will all of this impact his ability (or lack of ability) to handle interaction in typical boy sporting situations?

A: A very simple way of explaining processing speed is the length of time it takes for the information to be decoded (or understood/ interpreted) by the brain for a response to be made. When any information is processed, it is affected both ways while receiving and sending out information. For instance, when you give instructions to a child (who is at an age to understand & respond), instead of working on the task immediately, the child may look puzzled for some time until they are able to process the instructions to perform the task.

GAI (General Ability index) which is based only on two subsets of the WISC, which is the Verbal Comprehension Index (VCI) and the Perceptual Reasoning Index (PRI), hence not taking into account the Working Memory Index (WMI) and the Processing Speed Index (PSI). Children with learning disabilities, attention problems, or other neuropsychological issues may result in working memory and processing speed deficiencies which in turn lower the FSIQ (Full Scale IQ). Therefore, the GAI may provide a comparable approximation of overall intellectual ability as represented by the FSIQ for this group of children. So, when the processing speed is included, the overall intelligence quotient would be lowered.

There has been evidence suggesting that low scores on PSI might indicate ADHD. ADHD, with or without hyperactivity, does appear to affect both processing speed and working memory. If the child has ADHD, there is evidence that medication can increase processing speed. Because the processing speed test on the WISC-IV is heavily influenced by fine motor skills, if the child has dysgraphia that may bring down his scores.

As much as we are not able to treat the processing speed of a child, it can and should be accommodated. The brain is able to change itself or to be changed via intervention using different avenues (we call this neuroplasticity). Therefore, I believe that processing speed can be increased with meaningful, intense, and sustained work.

A good book on this is The Brain That Changes Itself by Norman Doidge. You may want to check this out to help the child. Also, the Brain Builder software from

Really depending on his other difficulties (ADHD etc), this may have some impact on his interaction due to the lack of ability in processing information at a reasonable speed. However, practice can certainly help but some extra effort goes into it.

Hope that helps and best of luck!


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