Cognitive Modeling Suggests That Attentional Failures Drive Longer Stop-Signal Reaction Time Estimates in Attention Deficit/Hyperactivity Disorder

Weigard, Alexander; Heathcote, Andrew; Matzke, Dóra; Huang‐Pollock, Cynthia · 2019 · Clinical Psychological Science

DOI: 10.1177/2167702619838466

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Summary

This study investigates the mechanisms underlying response inhibition deficits in children with Attention Deficit/Hyperactivity Disorder (ADHD) by addressing limitations in the standard measurement of stop-signal reaction time (SSRT). Traditionally, mean SSRT is used as a primary metric for inhibitory control, but this method is biased by excessive positive skew in reaction time distributions and "trigger failures"—instances where the stop signal fails to initiate the inhibition process. The authors hypothesized that these factors, particularly trigger failures reflecting early attentional lapses rather than inhibitory inefficiency, drive the longer SSRT estimates observed in ADHD. To test this, the researchers applied a Bayesian parametric approach using an ex-Gaussian race model to data from 209 children with ADHD and 99 typically developing controls. This model estimates the entire distribution of SSRTs and explicitly accounts for the probability of trigger failures ($P_{TF}$) and go failures ($P_{GF}$), thereby controlling for the bias introduced by skewed go reaction times. The study utilized a modified version of the model to accommodate children with lower accuracy rates, ensuring a representative sample. Participants completed a stop-signal task where the stop-signal delay was dynamically adjusted via a staircase procedure. The results indicated that children with ADHD exhibited greater positive skew in both go reaction time and SSRT distributions compared to controls. Crucially, the analysis revealed that children with ADHD displayed significantly more frequent trigger failures. When the model accounted for this skew and the incidence of trigger failures, the estimated latency and variability of the stop process itself did not differ significantly between groups. This suggests that the longer mean SSRTs typically reported in ADHD literature are largely driven by attentional failures to trigger the inhibition process, rather than an inherent inefficiency in the top-down inhibitory control mechanism. These findings challenge the prevailing view that ADHD is characterized primarily by deficits in response inhibition efficiency. Instead, the study concludes that performance on the stop-signal task in children with ADHD reflects impairments in early perceptual or attentional processes. By distinguishing between the failure to trigger inhibition and the speed of inhibition, this cognitive modeling approach provides a more nuanced understanding of ADHD, suggesting that interventions and theoretical models should focus on attentional engagement and signal detection rather than solely on inhibitory control capacity.

Key finding

Children with ADHD display more frequent trigger failures on the stop-signal task, indicating that their stopping difficulties are driven by attentional failures rather than inefficiencies in the inhibitory control process.

Methodology

modeling

Sample size: 308

Provenance

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Topics

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• cognitive capacity variation