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Gap between WPPSI-IV and SB V Test Scores
By Inderbir Kaur Sandhu, Ph.D
Q: My 5.5 yr old daughter was evaluated individually for giftedness. She was given the WPPSI-IV and had FSIQ of 148, GAI of 147. In the subcategories, she was 99-99.9% (135-149) across the board. She maxed out in the BD of VSI, PM of WMI, and Ca of PSI.
They also gave her the SB V test at the same time. On this, her SS on the quantitative reasoning domain was 125.
Why the huge discrepancy between the WPPSI-IV score (148) and the SB V score (125)? What does this mean?
A: In essence, comparing the same versions of individual IQ tests, such as the Wechsler's to the SB, should be quite straightforward. But each test has its own strengths. Psychologists suggest that matching the test to the subject's strengths results in the most accurate IQ score. The current version of the WISC (both IV and V) is a strong test for verbally gifted children, with emphasis on knowledge gained from reading. This version of the WISC, however, is also heavily timed. Short-term memory and processing speed scales often lower the full scale IQ score for gifted children.
Due to this, psychologists are usually familiar with the alternate scoring, called the General Ability Index (GAI), in cases where the difference between the verbal scale and short term memory or processing speed scales exceed limits. The current version of the Stanford Binet, the SB-5, is stronger for non-verbal intelligence, and less heavily timed. Note that for the previous versions of both these tests, the common wisdom was exactly the opposite: e.g., use the WISC-III for non-verbal kids, and the SB-4 for verbal/ intelligence gifted kids.
Therefore, it can be concluded that any test can only measure a small portion of a person's competence. Hence, in reality, all tests underestimate children's abilities rather than overestimate them. It is nearly impossible to fake abstract reasoning at an advanced level. When a disabled child achieves two different IQ scores, the higher score is believed to be the best estimate of the child's potential. Gifted children should be estimated in the same manner. Speak to her testers to get a detailed interpretation of the scores. Results also depended on her level of readiness, fatigue, anxiety and rapport with the test administrator. Since she was subjected to two tests on the same day, it could well affect her performance especially with the second test.
Hope that helps clarify some doubts. For admission into advanced programmes, use the WPSSI-IV scores. Best wishes to you!
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