Thanks to Sonya Sobiesky of Psychology Today for quoting me in her insightful article on preschool aptitude and ERB (WPPSI) testing, Baby Steps to Harvard.

Sobiesky writes:

But how accurate is IQ testing for toddlers? The commonly used Wechsler Intelligence Scale evaluates verbal ability based on vocabulary size and clarity of speech. “If a speech therapist can help you with these skills, how is that testing intelligence?” says Emily Glickman of Abacus Guide Educational Consulting.

Researchers agree that measurement errors due to fussiness, hunger, and even how well a child likes her questioner are fairly common when testing preschoolers.

Glickman also notes that “a lot of psychological testing is your ability to copy things. I think that’s a test of exposure, not intelligence. If kids have had practice drawing, if they’ve learned about farm animals, they’re going to do better on the tests.”

IQ scores at age 3 do correlate strongly with IQ scores at age 21, Joseph Fagan of Case Western Reserve University has found. But results at the lower end of the scale may be the most useful: IQ tests were originally developed to differentiate normal children from those needing special education. An IQ of 130 versus 120, Fagan says, “is not going to make a big difference in how someone turns out.”