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Interpretation of the WISC-V

By Inderbir Kaur Sandhu, Ph.D

Q: My 7 year old son was tested for ADHD by a Psychologist and tested very high on 3 parts of the WISC-V but very low on 2 parts. (Scores below) The two sections that he was very low on were the Working Memory and the Processing Speed. The Psychologist did not score an overall IQ score. I have read online that he should maybe write the GAI (General Ability Index) test as it does not include working memory or processing speed? I am troubled by the very low scores but also wonder if he would be considered gifted? Any suggestions would be appreciated.

  • Verbal Comprehension - Percentile Rank 98 (Very Superior)

  • Visual Spatial - Percentile Rank 88 (High Average)

  • Fluid Reasoning - Percentile Rank 92 (Superior)

  • Working Memory - Percentile Rank 18 (Low Average)

  • Processing Speed - 6 Percentile Rank (Borderline)

A: For an overall FSIQ score, it would include subtests Similarities, Vocabulary, Block Design, Matrix Reasoning, Figure Weights, Digit Span and Coding. This means both Verbal Comprehension and Fluid Reasoning subtests, and one each from Visual Spatial, Working Memory, and Processing Speed. The core indices will only require two subtests for an Index score. This also means that the Cognitive Proficiency subtests will have less weight, and only two subtests in the FSIQ have a significant speed element.

(Note: The main difference between WISC-IV is that in WISC-V, the PRI has been split into two indices, the Visual-Spatial and Fluid Reasoning Indices plus the addition of a few ancillary subtests)

It is indicated that in comparison to the WISC–IV FSIQ, the WISC–V FSIQ assigns a relatively lighter weight to working memory and processing speed abilities (only one subtest from each domain is included). Therefore, overall less emphasis is placed on working memory and processing speed. The psychologist probably did not put an overall score because there would be a statistically and clinically significant discrepancy in your son's profile that the FSIQ does not represent a unitary construct. But the score may still be valid. The FSIQ may not tell you everything that you need to know to cater the needs for your son. In your son's case, a GAI score may be appropriate. The GAI score would provide an estimate of general ability that is less reliant on working memory and processing speed compared with the FSIQ, in this case, may be suited for your son.

Children with neurodevelopmental disorders (such as learning disabilities, ADHD, Language Disorder, or autism spectrum disorder) have been associated with difficulties in working memory and processing speed and may obtain lower FSIQ scores. This makes the FSIQ score less meaningful. The GAI was developed to help with the identification of relative strengths and weaknesses that are based on comparisons between general ability and other cognitive functions. Compared with the FSIQ, the GAI provides an estimate of general intellectual ability that is less sensitive to the influence of working memory and processing speed by excluding those subtests. I am not sure why the GAI was not reported.

It may be a good idea for you to check with the psychologist and get more details on the breakdown of the scores and interpretation. Usually the cut-off point for gifted education is at 130 onwards but also depends on school districts and various other factors. These days a combination of assessments is used to determine children who are best suited in a gifted placement programme.

All the best.


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