Reaction Time Distribution Analysis of Neuropsychological Performance in an ADHD Sample

Abstract

Differences in reaction time (RT) variability have been documented between children with and without Attention Deficit Hyperactivity Disorder (ADHD). Most previous research has utilized estimates of normal distributions to examine variability. Using a nontraditional approach, the present study evaluated RT distributions on the Conners’ Continuous Performance Test in children and adolescents from the Multimodal Treatment Study of ADHD sample compared to a matched sample of normal controls (n = 65 pairs). The ex-Gaussian curve was used to model RT and RT variability. Children with ADHD demonstrated faster RT associated with the normal portion of the curve and a greater proportion of abnormally slow responses associated with the exponential portion of the curve. These results contradict previous interpretation that children with ADHD have slower than normal responding and demonstrate why slower RT is found when estimates of variability assume normal Gaussian distributions. Further, results of this study suggest that the greater number of abnormally long RTs of children with ADHD reflect attentional lapses on some but not all trials. The MTA is a cooperative treatment study performed by six independent research teams in collaboration with the staff of the Division of Clinical and Treatment Research of the National Institute of Mental Health (NIMH), Rockville, Maryland and the Office of Special Education Programs (OSEP) of the U.S. Department of Education (DOE). The NIMH Principal Collaborators are Peter S. Jensen, M.D., L. Eugene Arnold, M.Ed., M.D., John E. Richters, Ph.D., Joanne B. Severe, M.S., Donald Vereen, M.D., and Benedetto Vitiello, M.D. Principal Investigators and coinvestigators from the six sites are as follows: University of California at Berkeley/San Francisco (UO1 MH50461): Stephen P. Hinshaw, Ph.D., Glen R. Elliott, M.D., Ph.D.; Duke University (UO1 MH50447): C. Keith Conners, Ph.D., Karen C. Wells, Ph.D., John S. March, M.D., M.P.H.; University of California at Irvine/Los Angeles (UO1 MH50440): James M. Swanson, Ph.D.; Dennis P. Cantwell, M.D.; Timothy Wigal, Ph.D.; Long Island Jewish Medical Center/Montreal Children's Hospital (UO1 MH50453): Howard B. Abikoff, Ph.D., Lily Hechtman, M.D.; New York State Psychiatric Institute/Columbia University/Mount Sinai Medical Center (UO1 MH50454): Laurence L. Greenhill, M.D., Jeffrey H. Newcorn, M.D.; University of Pittsburgh (UO1 MH50467): William E. Pelham, Ph.D., Betsy Hoza, Ph.D. Helena C. Kraemer, Ph.D. (Stanford University) is statistical and design consultant. The OSEP/DOE Principal Collaborator is Thomas Hanley, Ed.D. Aaron Hervey, Ph.D. was supported on this project by a midcareer development award to the second author (K24 MH64478).