This study investigated the cognitive effects of stimulant medication in children with Attention- Deficit/Hyperactivity Disorder (ADHD). Shown below are data for the Connors' Continuous Performance Test (CPT) for 15 children diagnosed with ADHD. This is a visual vigilance task that requires the child to respond to the computer screen any time they see any letter other than "X". An overall index is calculated hat can be used to indicate attention problems based on reaction time, omission errors, and variability of esponses. A higher number indicates more problems with attention. Children were given various daily dosages of a drug methylphenidate (MPH) - given 0, 5mg, 10mg, and 5mg). The order of doses was counterbalanced so that all children received all doses at one point in the experiment. The children were on each dose one week before taking the CPT test (so each child took the est four times). OMG 5 MG 10 MG 25 MG 11 9 11 10 10 7 9 10 11 10 10 9 10 9 10 11 9 7 9 8 7 8 8 10 11 10 10