True IQBy Inderbir Kaur Sandhu, Ph.D
Q: I have three children, identical twins 22, and one 16 all boys. They were all diagnosed in school with learning disabilities. The twins verbal IQ's were both 128 but performance IQ was 95. Their disability was in auditory. My youngest verbal IQ is 133 and performance IQ was 91. And he has disability in visual.
What is the true IQ? Is it the higher number or somewhere in between? Incidentally, the Twins both go to Art Center College of Design in Pasadena and are considered very gifted. I'm struggling getting the youngest one through high school.
A: To date, there is no test that can actually predict true IQ. IQ scores are the best possible approximation to predict one's cognitive ability based on what is being tested. In fact it is indeed easier to make an IQ score that is lower than one's true IQ than it is to make a score that is higher. For example, taking a test on a bad day, or spending too much time on a few difficult items could actually artificially lower one's score. The best results are obtained when more than one test is administered.
In general, learning disability may be diagnosed when an individual's potential (IQ) differs significantly from their achievement. The measurement may be lower than his true IQ because of the test's inability to account for impairment on the part of the taker. For someone who is learning disabled, a good diagnosis takes a minimum of six hours, preferably 8 to10 by a trained psychologist. It consists of an intelligence test and an achievement test. This is really where it starts. The IQ score should not be influenced by the presence of learning disability.
People with learning disability often have a score profile where, for example, they score high on the math, but low on the verbal parts of the test. The diagnostician should then, based on that profile, select another IQ test (for example, a non-verbal one) that is insensitive to the presumed disability (in your son's case, visual disability), in order to get a reliable estimate of the "true" IQ. Your son's verbal scores are above average, and he may be gifted. You did not indicate the problems he faces at school, hence you may want to speak to a school authority (perhaps a school counselor if his problem is emotionally linked) on how best to help your son.
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