Adults and children with attention-deficit hyperactivity disorder (ADHD) often exhibit patterns of behavior that are different from individuals without ADHD. They tend to be more impulsive, have less focused attention, and take more risks. Tests that measure inhibitory control and attention can require subjects to respond rapidly to risk/reward scenarios. Other assessment tools used to gauge symptoms of inattention in ADHD prompt subjects to answer questions that are posed one after the other. All of these methods explore levels of cognitive functioning, processing speed, and working memory. But in a recent study, Walter Roberts of the Department of Psychology at the University of Kentucky posed a different question.
Roberts theorized that perhaps the impulsivity and inattention associated with ADHD were not merely the result of impaired cognitive ability, but inability to multitask due to decreased response capacity. To test this theory, Roberts conducted a study comparing 33 individuals without ADHD to 38 with ADHD in two separate tasks. The first task was designed to demonstrate response-selection ability, while the second test measured working memory. Together, the two tasks captured how well the participants responded under increased processing burdens. Roberts found that as the cognitive load became greater, the performance of both groups decreased. In the first task, the decline was more evident in the participants with ADHD, which suggests that these individuals have deficits in response-selection resources.
When Roberts assessed each group on the working-memory task, however, he found virtually no difference in their performance with respect to accuracy, but the ADHD group did take longer to respond. This could reveal a task-switching impairment in those with ADHD. Also, as the time between memory tasks decreased, the performance decreased for the ADHD group. These results show that although multitasking is one mechanism that appears to be negatively affected in people with ADHD, overall memory capacity is not. “This limited processing capacity may have implications for understanding cognitive dysfunction in adults with ADHD,” Roberts said. For example, maintaining employment requires constant cognitive task-switching, making it potentially more difficult for people with ADHD than for those without. Comprehending oral and written material in classroom settings could also deplete processing capacity and result in academic challenges for children with ADHD. Roberts hopes the results of his study will open the door for further exploration into the factors that could contribute to cognitive and behavioral impairments in those with ADHD.
Roberts, Walter, Richard Milich, and Mark T. Filmore. Constraints on information processing capacity in adults with ADHD. Neuropsychology 26.6 (2012): 695-703. Print.
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