Processing Speed and General Ability Index (GAI)
By Inderbir Kaur Sandhu, Ph.D
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
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
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!