Attention deficit hyperactivity disorder (ADHD) is characterized by poor adaptation of behavior to environmental demands, including difficulties in flexibly regulating behavior. To understand whether ADHD is associated with a reduction of strategic flexibility in modulating speed and accuracy, we used a perceptual decision-making task that required participants to randomly stress either fast or accurate responding. Thirty-one drug-free boys with ADHD combined-type (mean age: 10.2 years) and 33 healthy control boys (mean age: 10.7 years), matched for age and IQ, participated. Both reaction time and accuracy data were analyzed. Our findings demonstrated significantly lower accuracy in ADHD children than in controls when switching from speed to accuracy instructions. This deficit was directly associated with hyperactivity symptoms but not with inattention. Our results showed that ADHD is associated with a deficit in dynamically switching response strategy according to task demands on a trial-to-trial basis. (JINS, 2013, 19, 1–5)

Speed-accuracy instructions were manipulated in two symbolic stimulus-response compatibility tasks in an event-related potential study with young adults. For both tasks, the stimuli were the words left and right written in upper and lower case. Three late positive peaks (early P3, P3b, and P4) were seen in one task (with compatibility type blocked) with an additional peak (P3c) in the task that required identifying two stimulus attributes (compatibility type signaled by case). In both tasks, stimulus-response incompatibility and an emphasis on accuracy increased reaction time, made the P4 more prominent and increased its latency. With very rapid responding, P4 was not prominent because of overlap with the preceding peak. Functional characteristics of the peaks are discussed as well as potential sources of latency and amplitude measurement error when P3b is measured in a temporal window broad enough to include the P4.