How is Intelligence Measured?
By Dr. Kenneth Shore
Intelligence is measured by either a group or individually administered test. Not all tests that claim to measure intelligence, however, are of equal validity. Group intelligence tests, which are administered to a group of students with minimal examiner-examinee interaction, are useful screening devices at best, and their results should be interpreted with caution. Individual intelligence or IQ tests, administered on a one-to-one basis by a psychologist, are the preferred way to measure intelligence.
Typically individual tests of intelligence take an hour to an hour and a half to administer and are given by psychologists. These measures of learning aptitude typically encompass a range of cognitive tasks of a verbal, conceptual, perceptual and quantitative nature. They usually yield either an intelligence quotient (IQ), which compares your child’s performance with those of children of the same, or a mental age, suggesting that your child’s test performance is comparable to that of an “average” child of that age.
The IQ is the more common indicator used to assess intelligence. Most intelligence tests also have scale scores and subtest scores that allow for greater precision in the interpretation of results and identification of strengths and weaknesses. IQ scores typically range from 40 to 160, with 100 as the norm. Scores below 90 are considered below average; scores of 110 or above are considered above average.
The most common individual intelligence test used by psychologists is the Wechsler Intelligence Scale for Children. Used with children from six to sixteen, this test consists of for scales, including a Verbal Scale, a Performance Scale, a Memory Scale, and a Processing Speed Scale. Each scale contains subtests, which are scored on a scale from 1 to 19, with 10 the average score.
Scores are sometimes reported in terms of ranges and percentiles. For example, a psychological report may say that “Sarah is currently functioning in the ‘high average’ range of intellectual ability, equivalent to a percentile rank of 78 when compared to her peers nationally.” This means that on this particular test, Sarah scored equal to or better than 78 percent of the students her age.
When considering intelligence test scores, it is important to bear in mind that they offer only a limited picture of your child’s intellectual abilities. Also recognize that intelligence tests do not assess of number of factors related to academic, social and vocational success. They tell you little about your child’s social skills or emotional maturity and provide minimal information about his creativity, arguably a central component of intelligence. As a result, it is important to supplement intelligence test results with assessments of other skills.