On the Myth and the Reality of the Long-Term Stability of French WISC-IV Scores

Tests of intelligence are often used for diagnostics and intervention purposes. Beyond these goals, tests of intelligence are used to identify cognitive strengths and weaknesses. These diagnostic applications are based on the hypothesis that intelligence is an enduring trait. While several studies have investigated short-term stability of intelligence tests scores, few have assessed the long-term stability of tests scores. However, it is essential that diagnostics and intervention are based on stable intelligence tests scores. The objective of this study was to investigate the long-term stability of the French Wechsler intelligence scale for Children – Fourth Edition (WISC-IV) with non-clinical children. To achieve this goal, a test-retest procedure was used. The WISC-IV was administered twice to 250 non-clinical children aged from 7 to 12 years, with an average test-retest interval of 1.84 years (range 1.09 – 3.33). The long-term stability was analyzed according to interindividual stability (mean level of change and stability coefficient: correlation between test and retest scores) and intra-individual stability (individual difference in change). Individual changes in WISC-IV scores across the retest interval is presented within standard error of measurement. A two-standard errors of measurement (±2-SEM) interval was used to assess intraindividual stability/changes of the scores. As expected, test-retest coefficients were acceptable for FSIQ, VCI, PRI and GAI scores (r = .81, .80, .71 and .82, respectively). This finding was consistent with the hypothesis that intelligence is an enduring trait. Regarding intraindividual stability, results indicated that agreement based on the ± 2-SEM criterion was good for GAI and PRI. This idiographic comparison demonstrated that GAI and PRI were stable for more than 70% of children. Results indicated that WISC-IV scores were relatively stable (FSIQ, PRI, GAI), and hence that intelligence is stable over time. Individual changes revealed that only GAI and PRI were sufficiently stable for use with children