Flaws in Flynn Effect Research With the Wechsler Scales

Many Flynn effect (FE) studies compare scores across different editions of Wechsler's IQ tests. When construct changes are introduced by the test developers in the new edition, however, the presumed generational effects are difficult to untangle from changes due to test content. To remove this confound, we use the same edition of Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) across an 11-year period. Whereas previous research has reported the FE to be less than half the theoretical rate when comparing WISC-IV with Wechsler Intelligence Scale for Children-Fifth Edition (WISC-V), we find the rate of gain to be nearly identical to Flynn's prediction when comparing only WISC-IV scores over the same time period. The FE is shown to vary significantly across the domains of cognitive ability, and thus changes to the construct coverage of the WISC-V Full Scale IQ (FSIQ) composite between editions significantly affect FE findings. Implications for future FE research are discussed.