For as long as there's been an IQ test, there's been controversy over what it measures. Do IQ scores capture a person's intellectual capacity, which supposedly remains stable over time? Or is the Intelligent Quotient exam really an achievement test — similar to the S.A.T. — that's subject to fluctuations in scores?

Stephen Ceci, the Helen L. Carr Professor of Developmental Psychology, comments on a study finding that adolescent intelligence is likely not hard-wired but fluctuates over time.  Listen to the NPR Morning Edition story or read the transcript