Gifted Issues Discussion homepage Forums Identification, Testing & Assessment Most accurate- FSIQ, GAI, GAI with extended norms?

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All IQ tests that purport to provide a so-called "quotient IQ," derived by dividing one's "mental age" by his or her "chronological age" are defunct measures of intelligence. Extant IQ tests rely on deviation IQ, which is based on one's z score (the amount of deviation he or she has from the mean). The present day understanding of g is akin to the understanding of the gene between the time of Gregor Mendel and the discovery of the DNA double helix by Watson and Crick; we know that g exists empirically due to the correlation between any and all mental abilities, no matter how diverse. However, we do not know what it is that physiologically causes for g, although it must be a property or properties of the brain that are involved in all thoughts involving a conscious choice. According to Dr. Arthur Jensen, who passed away in late October of 2012, with a concerted effort from pyschometricians and stable funding, this problem may be solved in the next one or two decades.

That being said, such classifications as "gifted" and "superior" are not meant to pigeonhole the subject, but instead provide an argot that is accessible to both the clinician and layperson alike, and it is known that all IQ tests will measure the g-factor in addition to a sort of "fudge-factor" of non-g factors; the more tests one administers with higher g-loadings and ever more differing mental abilities, the more one minimizes this fudge-factor and measures g more accurately.

Although I am not familiar with the vast welter of IQ tests available, the Wechsler intelligence tests are the most widely used IQ tests at the moment. They are excellently normed, and in certain age groups measure full-scale IQ up to 210 for the WISC-IV. I would also prefer the WAIS-IV over the WAIS-III for other reasons; the addition of "digit span sequencing" has made the digit span task much more highly g-loaded (the g-loading of digit span on the WAIS-IV is 0.72, as compared to 0.59 for the WAIS-III). Arithmetic on the WAIS-IV has also been made to include simpler but longer calculations, therefore increasing its working memory demands and g-loading. Also, the WAIS-IV measures full-scale IQ up to 160, as compared to 155 for the WAIS-III.

In general however, many of the IQ tests in present use (such as the Stanford-Binet, Woodcock-Johnson, Differential Abilities Scale, Cognitive Abilities Test, Otis-Gamma Test, and so on and so forth) are easily capable of assessing IQ's several standard deviations from the mean, and a child who scored a full-scale IQ of 130 or more did not attain such a score through luck or "having a good day," etc.