Elongated tau for vocal articulation in children with ADHD

Slower and more variable reaction time (RT) is one of the most prominent cognitive signatures in childhood Attention Deficit Hyperactivity Disorder (ADHD). However, standard use of tasks that involve motor responses to index “speed” potentially confounds fine-motor coordination with central cognitive processing speed. One promising alternative is a vocal articulation task, which provides a measure of speeded performance that is independent of fine-motor coordination. The current study applies an ex-Gaussian decomposition to preparatory interval (the time to initiate a vocal response) and speech rate on a speeded articulation task among children with and without ADHD. Although differences in mean vocal response time were not found, there was substantial evidence that the tail of the distribution, as indexed by the tau parameter (which is linked to the rate of information accumulation), was larger in children with ADHD. Variance in tau was also greater among children with ADHD, and the greater variance was not fully explained by individual differences in working memory capacity. Results highlight the importance of adopting analytic methods that can more accurately describe performance.