title: ADHD performance reflects inefficient but not impulsive information processing: a diffusion model analysis.
abstract: OBJECTIVE
  Attention-deficit/hyperactivity disorder (ADHD) is associated with performance deficits across a broad range of tasks. Although individual tasks are designed to tap specific cognitive functions (e.g., memory, inhibition, planning, etc.), these deficits could also reflect general effects related to either inefficient or impulsive information processing or both. These two components cannot be isolated from each other on the basis of classical analysis in which mean reaction time (RT) and mean accuracy are handled separately.
  
  
  METHODS
  Seventy children with a diagnosis of combined type ADHD and 50 healthy controls (between 6 and 17 years) performed two tasks: a simple two-choice RT (2-CRT) task and a conflict control task (CCT) that required higher levels of executive control. RT and errors were analyzed using the Ratcliff diffusion model, which divides decisional time into separate estimates of information processing efficiency (called "drift rate") and speed-accuracy tradeoff (SATO, called "boundary"). The model also provides an estimate of general nondecisional time.
  
  
  RESULTS
  Results were the same for both tasks independent of executive load. ADHD was associated with lower drift rate and less nondecisional time. The groups did not differ in terms of boundary parameter estimates.
  
  
  CONCLUSIONS
  RT and accuracy performance in ADHD appears to reflect inefficient rather than impulsive information processing, an effect independent of executive function load. The results are consistent with models in which basic information processing deficits make an important contribution to the ADHD cognitive phenotype.
authors.affiliation: Faculty of Psychology and Educational Sciences, Department of Experimental-Clinical and Health Psychology, Ghent University, Ghent, Belgium. baris.metin@ugent.be
authors.forename: Baris
authors.initials: B
authors.lastname: Metin
authors.forename: Herbert
authors.initials: H
authors.lastname: Roeyers
authors.forename: Jan R
authors.initials: JR
authors.lastname: Wiersema
authors.forename: Jaap J
authors.initials: JJ
authors.lastname: van der Meere
authors.forename: Margaret
authors.initials: M
authors.lastname: Thompson
authors.forename: Edmund
authors.initials: E
authors.lastname: Sonuga-Barke
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000523:psychology; D002648:Child; D002755:Choice Behavior / Q000502:physiology; D003072:Cognition Disorders / Q000209:etiology*; D003220:Conflict, Psychological; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time / Q000502:physiology