Planning ability in adults with attention-deficit/hyperactivity disorder

Planning ability was investigated in 26 patients diagnosed with attention-deficit/hyperactivity disorder in adulthood and in 27 control participants, with groups matched for age, predicted IQ, and social class. They were tested using the 3-dimensional computerized Tower of London Test (Morris, Ahmed, Syed, & Toone, 1993; Morris, Rushe, Woodruffe, & Murray, 1995), which measures planning latencies as well as accuracy, with problems increasing in graded difficulty. For the control group, planning latencies increased systematically with task difficulty, with the participants slowing their initial responses to ensure accuracy. For those with attention-deficit/hyperactivity disorder, there was no increase in planning time and a corresponding diminution in accuracy on the most difficult problems. This pattern of impairment is interpreted as resulting from failure to inhibit responses when confronted with problem solving, leading to reduced planning activity.