Temporal predictability enhances response inhibition in adults with attention-deficit/hyperactivity disorder (ADHD)

OBJECTIVES: Individuals with ADHD have difficulty providing precise estimates of time. Nevertheless, they may still be able to harness temporally predictable information to guide behavior and regulate action control. We therefore examined whether temporal cueing improves impulse control or, conversely, exacerbates impulsive tendencies, in adults with ADHD. METHODS: Adults with ADHD and matched controls performed a temporally cued Simon task. Target onset time was either predictable or unpredictable, and lateralized responses were either compatible or incompatible with target location. Analysis of reaction time (RT) distributions allowed us to decompose impulsive behavior into two key elements: the initial urge to react impulsively and the top-down suppression of these impulses. Individual differences in attention and impulsivity were assessed using a Continuous Performance Test (CPT). RESULTS: Temporal cueing increased fast impulsive errors in both groups. However, temporal cues sped responses to compatible targets in controls but to incompatible targets in adults with ADHD. Distributional analyses revealed that although temporal predictability reduced inhibitory efficiency over time in controls, it actually improved the late-stage engagement of inhibitory processes in adults with ADHD. Furthermore, in the clinical group, greater RT variability in the CPT - reflecting attentional instability - was associated with larger cueing benefits, whereas higher CPT commission errors predicted weaker benefits. CONCLUSIONS: By compensating for endogenous deficits in action control, temporal cues facilitated top-down suppression of impulsive responses, particularly in individuals with high attentional instability. Our findings demonstrate that temporal predictability can act as a functional scaffold for inhibitory control in ADHD.