A Q&A on IQ tests

WASHINGTON—Many school districts don't immediately buy the latest versions of IQ tests when they're published. That's because they're expensive, the old tests seem to work just fine and their school psychologists are used to administering and scoring the old ones.

That can work out to your child's advantage—or disadvantage, according to Stephen Ceci, a professor of developmental psychology at Cornell University who's studied the consequences of using old IQ tests. He explains why in the questions and answers that follow.

Q. Why does the test's age matter?

A. New tests are always harder than older tests. For every year after a test is updated, a child's IQ score is inflated by three-tenths of a point. If the test is 10 years old, the inflation is about 3 points. If it's 20 years old, it's 6 points.

Q. What's wrong with that?

A. An older test can prevent kids who need special educational services from qualifying for them if it lifts their scores above the cutoff for eligibility for special education classes. A new test can make IQ scores appear to plummet by comparison with prior years' results. It can even influence admission into gifted and talented programs.

Q. How so?

A. Suppose your child was eligible for a gifted/talented program some years ago when she was last tested but recently was retested and told she'd scored a little too low. Perhaps her performance was unchanged but her score seemed to drop because a new test was used for the second administration. Whenever a new test is used, there's a significant drop in IQ score, often 5 or 6 points. In fact, the same child taking two versions of the test on the same day will generally score 5 or 6 points higher on the older version.

Q. How might an old test be disadvantageous in a special-education placement?

A. Suppose a child has serious learning problems and would benefit from small classes and intensive instruction. Often, those classes are available only to students whose IQ scores are below 70. If a test is old, a child with a true IQ of, say 67, may appear to have an IQ of, say, 73.

Q. What can a parent do?

A. Ask which test battery was used or will be used. Ask what the "norming date" is, meaning the year when the test was last adjusted to account for changes in average IQ. If it's not the latest version of the test, ask the administrator why. Then ask whether they'll be adjusting the scores in any way.

Q. How do I know what the latest norming dates are?

A. For the Wechsler Intelligence Scale for Children, the latest test is the WISC-IV, released in 2003. The WISC-III came out in 1991. For the Stanford-Binet Fifth Edition the date is 2003. For the Stanford-Binet Fourth, it's 1986.