Construct and predictive validity of inattention and impulsivity/hyperactivity

This study examined the construct validity of the current model of ADHD. A multi-trait multi-method procedure (MTMM) was utilized to determine the extent to which inattention and impulsivity/hyperactivity occur independently of the method employed to assess the constructs. The predictive validity of the constructs, as operationalized by the Behavior Assessment System for Children (BASC) inattention subscale, BASC hyperactivity subscale, Auditory Continuous Performance Test (ACPT) omission error score, ACPT commission error score and the Freedom from Distractibility Index, for school achievement was also addressed.

Participants included 112 children ranging in age from 6 years to 11 years. Construct validity was investigated by using two methods of assessment to measure the two traits; inattention and impulsivity/hyperactivity. The BASC rating scale was used as a subjective measure and the ACPT was used as an objective measure. Results from the MTMM matrix failed to produce compelling evidence for the construct validity of the current model of ADHD. Specifically, results of this study suggest that although there is a significant amount of variance explained by the traits, there is a greater amount of shared variance between similar methods of measurement than traits. Therefore, the method of assessment (rating scale versus objective measure) may explain more of the variance within the data than the theoretical constructs.

Results of the multiple regression analyses indicated that the Freedom from Distractibility Index was consistently the most significant predictor of academic achievement in areas of basic reading, reading comprehension, math calculation and spelling skills. Surprisingly, the ACPT omission error score was found to be a significant predictor for spelling, basic reading and math calculation skill. Rating scales did not prove to be significant predictors of academic achievement.

In conclusion, this study did not find the theoretical constructs of inattention and impulsivity/hyperactivity to be robust. Therefore, assessment specialists should be aware that assessment results may be partly a function of the type of instrument used. Results of the multiple regression analyses provided evidence that the Freedom from Distractibility Index is the strongest predictor for academic achievement. The ACPT omission score emerged as a statistically significant predictor although it added only a relatively small amount of the variance predicted by the equation. The rating scales were not significant predictors for academic performance.