title: Evidence for higher reaction time variability for children with ADHD on a range of cognitive tasks including reward and event rate manipulations.
abstract: OBJECTIVE
  The purpose of the research study was to examine the manifestation of variability in reaction times (RT) in children with attention deficit hyperactivity disorder (ADHD) and to examine whether RT variability presented differently across a variety of neuropsychological tasks, was present across the two most common ADHD subtypes, and whether it was affected by reward and event rate (ER) manipulations.
  
  
  METHODS
  Children with ADHD-combined type (n = 51), ADHD-predominantly inattentive type (n = 53), and 47 controls completed five neuropsychological tasks (Choice Discrimination Task, Child Attentional Network Task, Go/No-Go task, Stop Signal Task, and N-back task), each allowing trial-by-trial assessment of RTs. Multiple indicators of RT variability including RT standard deviation, coefficient of variation and ex-Gaussian tau were used.
  
  
  RESULTS
  Children with ADHD demonstrated greater RT variability than controls across all five tasks as measured by the ex-Gaussian indicator tau. There were minimal differences in RT variability across the ADHD subtypes. Children with ADHD also had poorer task accuracy than controls across all tasks except the Choice Discrimination task. Although ER and reward manipulations did affect children's RT variability and task accuracy, these manipulations largely did not differentially affect children with ADHD compared to controls. RT variability and task accuracy were highly correlated across tasks. Removing variance attributable to RT variability from task accuracy did not appreciably affect between-groups differences in task accuracy.
  
  
  CONCLUSIONS
  High RT variability is a ubiquitous and robust phenomenon in children with ADHD.
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Jeffery N
authors.initials: JN
authors.lastname: Epstein
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Langberg
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Rosen
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Amanda
authors.initials: A
authors.lastname: Graham
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Narad
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Tanya N
authors.initials: TN
authors.lastname: Antonini
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: William B
authors.initials: WB
authors.lastname: Brinkman
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Tanya
authors.initials: T
authors.lastname: Froehlich
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: John O
authors.initials: JO
authors.lastname: Simon
authors.affiliation: Department of Pediatrics, Cincinnati Children's Hospital Medical Center.
authors.forename: Mekibib
authors.initials: M
authors.lastname: Altaye
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications*; D002648:Child; D002755:Choice Behavior / Q000502:physiology; D003072:Cognition Disorders / Q000209:etiology*; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D015203:Reproducibility of Results; D012201:Reward