The WISC-IV is yielding many gifted-level scores at the Gifted Development Center. However, some of the Full Scale IQ scores are excessively lowered by Working Memory and Processing Speed scores. As intelligence is primarily abstract reasoning ability, emphasizing short-term auditory memory and processing speed on paper-and-pencil tests is less helpful. Two Working Memory subtests (only one was required on the WISC-III) and two Processing Speed subtests (only one was required on the WISC-III) place more weight on these processing skills in the Full Scale IQ score. This is unfortunate for gifted children and confounds the Full Scale IQ Score (FSIQ) as a gifted identifier.

In the normative sample for the WISC-IV, the gifted group (which had scored at least 130 previously) earned a Full Scale IQ score of 123.5 on the WISC-IV. Their Verbal Comprehension score was 124.7 and Perceptual Reasoning score was 120.4. However, in line with our experience, their Working Memory averaged only 112.5 and their Processing Speed was 110.6 (WISC-IV Technical Manual, p. 77).

The Increased Emphasis on Processing Skills

Perhaps the inclusion of more processing skills measures is appropriate for lower functioning children. If the child's processing speed on paper-and-pencil tasks is so slow that he or she cannot complete work in a reasonable amount of time in the classroom, processing speed may be such a limiting factor that it should be included in IQ scores. Likewise, if short-term auditory memory is so poor that the teacher's instructions can't be retained at all, this is a significant problem. However, gifted children rarely perform extremely poorly in these areas on an absolute scale. It makes much more sense to identify them as gifted based on assessments emphasizing reasoning, provide them gifted learning experiences, and then add any accommodations based on relative weaknesses to the gifted accommodations.

A Full Scale IQ score that averages gifted reasoning and average processing skills fails to identify either the giftedness or the relative weaknesses. Test authors have wrongly assumed that gifted children are fast processors. Some are very quick; others are reflective or perfectionistic, slowing their speed. Gifted children also show a preference for meaningful test materials, and may not perform well on short-term memory tests or other tasks that utilize non-meaningful material. They usually perform so much better with meaningful material that their scores with non-meaningful material are difficult to interpret.

The higher a child�s intelligence, the more reasonable it would be to assume that the child would score well in all four of the indices. However, as noted above, the gifted group in the normative sample scored in the superior ranges on Verbal Comprehension and Perceptual Reasoning, but considerably lower in Working Memory and Processing Speed. Presumably some group other than the gifted scored in the superior ranges in these two strands, but this introduces a confounding variable into the Full Scale IQ score. The two lower indices do not reflect the abilities of the gifted and tend to lower their Full Scale scores. Given these issues, it will be a challenge for testers of the gifted to choose tests appropriate to document gifted strengths and diagnose weaknesses, without eliminating children from gifted program entrance requirements.

JDax3 - if you google WISCIV GAI, you should see a download for the WISCIV report. If you don't see it, let me know. It then aids you in calculating the GAI.

From the posted scores, the GAI would be 148 (based on a VCI of 140, and a PRI of 139). This score falls above the 99.9th percentile.

So, PSI does have an impact and can 'skew' the results, if even just a bit.

Testers of the gifted know that abstract reasoning tasks best identify cognitive giftedness, while processing skills measures do not...
When the WISC-IV is used for the identification of gifted students, either the General Ability Index (GAI), which emphasizes reasoning ability, or the Full Scale IQ Score (FSIQ), should be acceptable for selection to gifted programs. The GAI should be derived using the table provided in the Harcourt Assessments website (Technical Report 4)

Flanagan and Kaufman (2004), in Essentials of WISC-IV Assessment, deem the FSIQ �not interpretable� if Composite scores vary by 23 points (1.5 standard deviations) or more.

I kind of wonder (not that I'm generally a conspiracy theorist) whether the folks at WISC designed their test specifically to reduce GT scores, thereby lowering the amount of people that are identified into public GT programs to save the schools money.

They also say:
My DS12 just took the WISC-IV. His PSI came out ~40 points lower than the other three. I'm trying to figure out what that really means. Not much luck in finding anything I believe so far. The math is all pretty fuzzy.
(JZ)

The IQ tests are designed to make the finest distinctions for most of the children taking the test (the 95% of children who fall between 70 and 130.) We are asking a test to make fine distinctions with a relatively blunt tool when we are looking at the extremes.