We compared the performance of children with ADHD and typically developing children on two temporal tasks, a bisection task and a reproduction task, in auditory and visual modalities. Children with ADHD presented a larger variability when performing auditory and visual temporal tasks. Moreover, they overestimated the durations in bisection tasks and underproduced duration intervals in the visual reproduction task. In the context of the pacemaker-accumulator model, these results suggest that temporal deficits might result from a dysfunction in the switch and/or memory impairment.

Objective: A deficit in interference control is commonly reported in children with attention deficit hyperactivity disorder (ADHD). This has mainly been interpreted as a difficulty in inhibiting inappropriate responses. However, it could be due to at least two distinct and independent processes, which are often confounded: the activation or suppression of impulsive responses. The aim of the present study was to separate the contribution of these two processes. Method: We compared performance of 26 children with ADHD to that of 26 non-ADHD children using a novel approach based on electromyographic activity (EMG) analysis. EMG allows two distinct indices to be computed: incorrect activation rate, which is an index of the intensity of impulse capture and correction rate, which provides a direct measure of the ability to suppress automatic responses. Results: Children with ADHD were slower, committed more errors, and had a larger interference effect than non-ADHD children. Moreover, we observed a greater incorrect activation rate and a lower correction rate in the ADHD group. Conclusions: Our data suggest that the difficulties in interference control found in children with ADHD are explained by both impaired inhibitory processes and a greater propensity to activate automatic responses.