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Low Scores in WISC IV Processing Speed

By Inderbir Kaur Sandhu, Ph.D

Q: We have a 6 year old son recently tested WISC IV:

GAI 159
Verbal Comprehension 146
Perceptual Reasoning 151
Working Memory 135
Processing Speed 85
Full Scale IQ 141

Processing speed seems to be the "odd one out"

1. Does this make sense, or could it be an artifact of motivation, and the test administration, which was done by someone experienced with low functioning kids, but certainly not with gifted kids.

My son used to have a tremendous eagerness to learn. Last summer he was adding 5 digit numbers in his head for entertainment. He started K last September and has been noticeably disappointed in the "math" classes, and lack of science teaching, which he had expected. He has verbalized this in a dejected tone of voice. I feel he is bored and is recently becoming oppositional.

He increased his reading rapidly in the past year, and now reads about one chapter book (currently, the Andrew Lost series) per day. He is able to tell about what he read.

2. Is rapidly learning to read, with good comprehension, compatible with slow processing speed?

3. Two years ago, he completed a number of Lego Technic structures; these are intended for 9-12 year olds and include a thick instruction manual and hundreds of pieces. He completed these in a number of hours each, working for an hour at a time, intensely, and without assistance. He used to cut out outlines of jet planes (with correct details of tail shape etc) or animals with quite remarkable dexterity, quickly moving the scissors around the finer parts of the outline. He has used scissors on his own for years.

Are these skills compatible with slow processing speed?

I feel he has become de-motivated at his school. They have steadfastly omitted to give him more challenging questions in math, for example (his math class consists of adding single digit numbers). However, the teacher pointedly related that he was unable to immediately apply his math skills to a problem which she asked him out loud, as part of a class project.

At home he enjoys doing long multiplication now (three digit numbers), and simple algebra e.g:

10 + 2n = 20
9 + 3n +  4n +  3 = 26

At first he tries to arrive at the answer in one fell swoop, but realized after some stubbornness that it is more effective to write out the working line by line.

Is this stubbornness a function of low processing speed or just that he feels he should be able to do it his way?

We are very much in need of help. Thank you so much.

A: Processing speed generally refers to the varying speed with which individuals are able to perform cognitive activities such as the recognition of simple stimuli. Higher speed in cognitive processing usually allows more information to be acquired in a shorter time span enabling the individual to absorb and master materials of higher levels. Above average individuals usually have high processing speed, thus enabling them to reach developmental milestones ahead of their age mates. In layman’s terms, the brain is working faster which is viewed as superior intelligence, hence the difference in human intelligence.

Having said that, there is more to intelligence than speed of processing, which is the reason most IQ test use a combination of factors to assess intellectual skills. According to the WISC, processing speed measures children's abilities to focus attention and quickly scan, discriminate between, and sequentially order visual information. It requires persistence and planning ability, but is sensitive to motivation, difficulty working under a time pressure, and motor coordination too. Cultural factors seem to have little impact on it. It is related to reading performance and development too. It is related to Working Memory in that increased processing speed can decrease the load placed on working memory, while decreased processing speed can impair the effectiveness of working memory.

In the case of your son, given your description, the PSI should have been higher. However, there may be other factors influencing the scores. It may be due to motivation but unlikely the test administration. Bear in mind that processing speed accounts for only 23% of the variance in general intelligence. Is there any indication of ADHD – the inattentive type? Apparently, lower processing speed scores could indicate such concerns. There are children with ADHD who have IQ scores in the gifted range, yet rather low processing speed. The WISC scores alone are not able to make that diagnosis. However, this may not even be the case for your son as his attention appears to be stable enabling him to accomplish tasks that you mentioned.

It is best that you speak to the tester regarding the interpretation of the scores. Based on the full report and breakdown of the scores (especially for coding), s/he may be able to help. If you are not satisfied with the explanation, look for someone experienced in testing gifted children who may be able to interpret the results better. Good luck!

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Essentials of WISC-IV Assessment
Dawn P. Flanagan Ph.D, Alan S. Kaufman Ph.D

The WISC-IV is the top intelligence assessment instrument for children in the US, providing essential information into a child's cognitive functioning. This book applies a new, expanded theory-based approach to interpreting the latest edition of the WISCŪ and provides beginning and seasoned clinicians with comprehensive step-by-step guidelines to administering, scoring, and interpreting this latest revision of the Wechsler Intelligence Scale for Children.

This book provides students and practitioners with an unparalleled resource for learning and application, including expert assessment of the test's relative strengths and weaknesses, valuable advice on its clinical applications, and illuminating case reports.

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