EVERYTHING YOU WANTED TO KNOW ABOUT INTELLIGENCE TESTING THAT NO ONE WOULD TELL YOU

EVERYTHING YOU WANTED TO KNOW

About Intelligence Testing that No One Would Tell You

By Marcia Eckerd, PhD

I FIND MOST PARENTS ARE CONFUSED BY THE INTELLIGENCE TESTING ADMINISTERED TO THEIR CHILDREN. IT’S EASY TO MISUNDERSTAND THE RESULTS IF YOU DON’T UNDERSTAND HOW THE TEST IS STRUCTURED AND YOU OVER-FOCUS ON THAT MAGIC IQ NUMBER. IN ADDITION TO UNDERSTANDING THE TEST ITSELF, YOU NEED TO KNOW A LITTLE ABOUT SCORING AND STATISTICS AND SOMETHING ABOUT PUTTING IT TOGETHER.

The Wechsler Intelligence Test for Children (WISC-V) is the “IQ” test for children six to 16. It’s considered the “gold standard” by most evaluators. It gives an overview of strengths and weaknesses in multiple areas and generally provides reasonable expectations of the child’s school performance. For children over 16, the Wechsler Adult Intelligence Test can be used (WAIS-IV), and for children two years and seven months old through seven years and seven months old, the Wechsler Preschool and Primary Test of Intelligence (WPPSIIV) can be used. There’s an age overlap; a bright six-year-old might get the WISC-V while a child suspected to have some

weaker skills might get the WPPSI-IV, and a 16-year-old with strong skills might get the WAIS-IV while another student might get the WISC-V. Your child’s age isn’t the only factor in deciding which test to administer.

It’s important to understand how the WISC-V (or any of the Wechsler tests) is structured. The WISC-V is actually made up of 10 subtests, yielding five Index Scale scores. Each Scale score measures a unique ability.

There are five Index Scales, each consisting of two subtests measuring different skills within the overall domain.

Name of WISC-V Index Scale Abilities Measured

Verbal Reasoning

Visual Spatial Knowledge of words and how to apply them in verbal concept formation, reasoning, and expression

Seeing visual details, understanding spatial relationships and construction abilities, and seeing the relationship between parts and a whole, involving visual and motor abilities

Fluid Reasoning

Working Memory Seeing a meaningful relationship among visual objects and applying that knowledge with conceptual reasoning

Attention, concentration and holding information in mind, and being able to use it

Processing Speed Speed and accuracy of visual scanning and identifying visual objects, short term memory, and visual-motor coordination

These scales are combined to yield the Full-Scale IQ. Many parents focus on the Full-Scale IQ, but it can be a meaningless number if the scales are inconsistent. Let’s say the Full-Scale IQ is average. It could mean that all the scales are in the average range, or, with an extreme example, you could have a superior Verbal Comprehension Index Scale and a low average or borderline Visual Spatial or Fluid Reasoning Index Scale if verbal skills were much stronger than visual skills. It’s like saying your temperature is average if your hair is on fire and your feet are in a bucket of water.

It’s important to know the Index Scale scores and what they measure to understand relative strengths and weaknesses and how they impact each other. A child with a superior verbal IQ might struggle in school with material visually presented (maps, charts, graphs) if the visual scales are lower. A child with a weak working memory score might have problems holding onto information verbally or visually presented, so if a teacher lectures or discusses material not in the book, this child may perform more poorly than expected. The child with poor working memory or processing speed might have trouble taking notes, which necessitates listening, holding information in memory and writing all at the same time.

You also want to look at the subtest scores within each Index Scale score: are they consistent? As an example, the Verbal Comprehension Index Scale includes two subtests: Vocabulary, which tests word knowledge, and Similarities, which tests the ability to form abstract concepts by understanding what two words (say bird and dog) have in common (both are animals). A child with strong word knowledge (perhaps good at memorizing words) who struggles with abstraction could have a high average Vocabulary subtest score, a low average Similarities subtest score, and an average Verbal Comprehension Index Scale. That average Verbal Comprehension score tells us very little; this child might be very good at memorizing information but struggles to use it conceptually.

The obvious question is, how can you know if the difference between scales or subtests is significant? IQ scores and Index Scale scores are standard scores, with a mean of 100 and a standard deviation of 15 scaled scores. Subtest scores have a mean of 10 and a standard deviation of three. The mean is the score considered average for your child’s age, and the standard deviation is how many points you need before you consider the difference between scores to be significant; a difference of more than a standard deviation is significant and should be examined. Most schools use the standard deviation to determine the description of the score, so a score between 100 and 85 is considered in the average range.

Some psychometric tales use a more stringent limit; 90 to 110 is average, for example. I use the psychometric table, so here’s a chart to guide you. This chart is based on standard scores, so those come out evenly, and the other scores have some overlap at the ends.

To understand your child’s WISC-V, you need to know the scores and not just the labels. Here’s where it gets interesting. If standard scores are consistent across indices and subtest scores are consistent within an Index Scale, that’s going to be a reliable estimate of the child’s ability. When the scores are inconsistent is when the difficulty occurs. Sometimes schools average scores together, which masks strengths and weaknesses. Obviously, the Full-Scale IQ is only meaningful if the Index Scales are consistent; as standard scores, that means they have to be less than 15 points different. You can’t go by descriptions like “average,” “high average,” or “low average” alone.

You also need to know the range of a standard score goes above and below the “middle” of the word describing a score. A standard score can be 85 and be considered “average” by a school, and another score can be 110 and still be called “average,” but they are more than 15 points apart. In that case, even though both are labeled “average,” you might ask about the relative difference. On the other hand, scores close to each other aren’t that different, so a score of 80 and a score of 90 aren’t too different even if one is called “low average” and the other is called “average.”

The bottom line is you want to look at the scores—the Index Scale scores and the subtest scores—to see if any Index Scales differ by 15 points or if subtests differ by three points to see if a student has strengths and weaknesses obscured by combining the numbers or just looking at labels. If there’s a significant difference, even if it’s between subtests, you want to understand what skills are being tested and if that might underlie difficulty for the child. A significant difference among Index Scores might indicate ADHD, LD, or some variation in the rate at which skills are maturing. Even a weakness in a subtest—for example, verbal conceptualization—could have a significant impact on your child’s performance and frustration level.

One caveat is that there’s more to life than intelligence tests. Speech and language therapists look at language skills in depth, academic testing picks up reading, math, or writing difficulties, and tests like the Behavior Rating Inventory of Executive Functions (BRIEF) rate those all-important executive functions. Many bright children have challenges not evident on the WISC-V.

The bottom line is there’s a lot of information in the WISC-V if you know to dig for it and ask questions, rather than just accepting, “He’s in the average range.” Understanding the structure of Index Scale scores and that there are subtext scores lets you look at domains separately so you can think about learning style. Is your child a better auditory or visual learner, or does some combination (or hands-on, using visual-motor reasoning) work best?

Standard score Percentile rank Scaled score Description

130—150 9—99+ 16—19 Very Superior 121—129 92—97 14—15 Superior 111—120 77—91 13—14 High Average 110—90 75—25 8—12 Average 80—89 9—23 6—7 Low Average 7—79 2—8 4—5 Borderline Below 70 Impaired

Marcia Eckerd, PhD, received a BA from Yale University, Magna Cum Laude, and a PhD from City University of NY. She has been in private practice since 1985 and has extensive training in neuropsychological evaluation, as well as providing therapy and consulting for patients of all ages with LD, ADHD, and autism spectrum disorder (ASD)/Asperger’s syndrome. Marcia writes and speaks extensively on ASD, executive functions, social skills, and anxiety/mindfulness. She has been appointed by the State Legislature of CT to serve on the CT ASD Advisory Council and is on the Clinical Advisory Group of AANE.org (Asperger/ Autism Network). She serves on the Professional Advisory Board of Smart Kids with LD as well as the community medical staff at Norwalk Hospital. She’s written multiple professional peer-reviewed journals on the diagnosis of autism and has also contributed to Autism Spectrum News, Autism Parenting Magazine, Psych Central, and Psychology Today.