Mean response times, variability, and skew in the responding of ADHD children: a response time distributional approach

Response time (RT) distributions from three fixed foreperiod conditions (2, 4, and 8 s) in a warned four-choice RT task were obtained for a group of b oys with attention-deficit/hyperactivity disorder, combined type (ADHD; n = 17) and for two groups of normal control boys (age-matched, n = 18, and yo unger-aged, n = 10). Quantitative measures of distributional shape were der ived by fitting the ex-Gaussian distributional model to the individual RT d ata. Statistical results indicate that the ADHD distributions differ from t he age-matched control distributions with respect to the size of the tail ( larger for the ADHD boys), but differ from the younger control distribution s with respect to the location of the leading edge (slower for the younger control boys). Receiver operating characteristic (ROC) results reveal that the ex-Gaussian exponential component is highly diagnostic of the ADHD boys . (C) 2000 Elsevier Science B.V. All rights reserved.