The model also explains the ratherdramatic fluctuation in symptoms across settings and tasks.The poor sustained attention that apparently characterizes those with ADHD probably represents an impairment in goal-or task-directed persistence arising from poor inhibition and the toll it takes on self-regulation. And the distractibility ascribed to those with ADHD most likely arises from poor interference control that allows other external and internal events to disrupt the executive functions that provide for self-control and task persistence.