Youth with attention deficit hyperactivity disorder (ADHD) often show reduced post-error slowing (PES) compared to typically developing controls. This finding has been interpreted as evidence that children with ADHD have error recognition and adaptive control impairments. However, several studies report mixed results regarding PES differences in ADHD, and among healthy controls, there is considerable debate about the cognitive-behavioral origin of PES.

We tested competing hypotheses aimed at clarifying whether reduced PES in children with ADHD is due to impaired error detection, deficits in adaptive control, and/or attention orienting to novelty. Children aged 7–11 years with a diagnosis of ADHD (n = 74) and controls (n = 30) completed four laboratory-based computer tasks with variable cognitive loads and error types.

ADHD diagnosis was associated with shorter PES only on a task with high cognitive load and low error-cuing, consistent with impaired error recognition. In contrast, there was no evidence of impaired adaptive control or heightened novelty orienting among children with ADHD.

The cognitive-behavioral origin of PES is multifactorial, but reduced PES among children with an ADHD diagnosis is due to impaired error recognition during cognitively demanding tasks. Behavioral interventions that scaffold error recognition may facilitate improved performance among children with ADHD.

Obsessive-compulsive disorder (OCD) is associated with an abnormally large error-related negativity (ERN), an electrophysiological measure of error monitoring in response to performance errors, but it is unclear if hoarding disorder (HD) also shows this abnormality. This study aimed to determine whether the neurophysiological mechanisms underlying error monitoring are similarly compromised in HD and OCD.

We used a visual flanker task to assess ERN in response to performance errors in 14 individuals with HD, 27 with OCD, 10 with HD+OCD, and 45 healthy controls (HC). Age-corrected performance and ERN amplitudes were examined using analyses of variance and planned pairwise group comparisons.

A main effect of hoarding on ERN (p = 0.031) was observed, indicating ERN amplitudes were attenuated in HD relative to non-HD subjects. A group × age interaction effect on ERN was also evident. In HD-positive subjects, ERN amplitude deficits were significantly greater in younger individuals (r = −0.479, p = 0.018), whereas there were no significant ERN changes with increasing age in OCD and HC participants.

The reduced ERN in HD relative to OCD and HC provides evidence that HD is neurobiologically distinct from OCD, and suggests that deficient error monitoring may be a core pathophysiological feature of HD. This effect was particularly prominent in younger HD participants, further suggesting that deficient error monitoring manifests most strongly early in the illness course and/or in individuals with a relatively early illness onset.