First, we’ll provide a little background on IQ tests: In 1955, American psychologist David Wechsler published an intelligence test that became known as the Wechsler Adult Intelligence Scale (WAIS). He defined intelligence as “the global capacity of a person to act purposefully, to think rationally, and to deal effectively with his environment.”
To measure this faculty, he created two sub-tests–one measuring “verbal intelligence” and the other, “non-verbal (performance) intelligence”. Assuming that intelligence is normally distributed, Wechsler mapped his test scale onto a normal distribution with mean 100 and standard deviation 15. By standardizing his tests in this way, Wechsler linked his scale directly to percentiles, allowing for immediate comparisons to average intelligence.
Wechsler’s departure from a single measure of intelligence offered by the Stanford-Binet test evolved from his recognition that intelligence may have more than one dimension. Growing recognition of these multiple dimensions led to subsequent revisions of the Wechsler tests to include measures of verbal comprehension, perceptional reasoning, working memory, and processing speed. WAIS-IV has 10 subtests and 5 supplemental tests that summarize intelligence with two measures–a final IQ score and a General Ability Index. IQ is a multi-dimensional measure of aptitudes for language and mathematics, as well as a host of related cognitive skills. Capabilities in abstract thinking, generalization, drawing inferences and identification of patterns in data are tested and scored. A verbal IQ of 133 indicates an exceptional language capability that is 2 standard deviations above average, while the performance IQ of 104 indicates that the performance in such things as eye-hand coordination (psychomotor skills) is about average. The full scale IQ of 121 is the weighted average of the scores on all the aptitudes measured and this score at 121 is in the 92nd percentile. This means that about 92% of the population scores less than 121 when all their cognitive skills are scored and combined into a single IQ score. The bottom line: Someone achieving these scores is gifted in language skills and average in the psychomotor area. However, if the person receiving these scores is a child, then it might mean that the child is significantly ahead of other children the same age, and the “giftedness” relative to others may or may not persist through to maturity.
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