Cited by 324Attention Deficit Hyperactivity DisorderNeural and Behavioral Psychology StudiesDevelopmental and Educational Neuropsychology

The DOI matches its Crossref record; 96 of the 114 references it cites were found in a registry or an index, and 18 are not checked yet; 2 of the 97 sources its claims cite were checked for support.

Reaction Time Variability in ADHD: A Review

Open access
Tamm, Leanne, Narad, Megan E., Antonini, Tanya N., O'Brien, Kathleen M., Hawk, Larry W., Epstein, Jeffery N.·2012·Neurotherapeutics

Abstract

For the past decade, intra-individual variability in reaction times on computerized tasks has become a central focus of cognitive research on Attention-Deficit/Hyperactivity Disorder (ADHD). Numerous studies document increased reaction time variability among children and adults with ADHD, relative to typically developing controls. However, direct comparisons with other disorders with heightened reaction time variability are virtually nonexistent, despite their potential to inform our understanding of the phenomenon. A growing literature examines the sensitivity of reaction time variability to theoretically and clinically relevant manipulations. There is strong evidence that stimulus treatment reduces reaction time variability during a range of cognitive tasks, but the literature is mixed regarding the impact of motivational incentives and variation in stimulus event rate. Most studies of reaction time variability implicitly assume that heightened reaction time variability reflects occasional lapses in attention, and the dominant neurophysiological interpretation suggests this variability is linked to intrusions of task-negative brain network activity during task performance. Work examining the behavioral and neurophysiological correlates of reaction time variability provides some support for these hypotheses, but considerably more work is needed in this area. Finally, because conclusions from each of domains reviewed are limited by the wide range of measures used to measure reaction time variability, this review highlights the need for increased attention to the cognitive and motivational context in which variability is assessed and recommends that future work always supplement macro-level variability indices with metrics that isolate particular components of reaction time variability.

Verified 2026-10-06 · 18 references not checked yet

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review synthesizes evidence that ADHD is associated with greater intra-individual reaction time variability across computerized tasks, with intermittent long responses as a key component. It argues that this variability is not specific to ADHD and that measurement choices, task context, and neurophysiological models need refinement.

Key findings

  • ADHD groups show higher reaction time variability than controls across working memory, attention, inhibitory control, and choice-discrimination tasks, in both children and adults; these differences are often larger than those seen on other neuropsychological indicators.
  • Elevated variability also occurs in autism, schizophrenia, bipolar disorder with psychotic symptoms, traumatic brain injury, early Alzheimer’s dementia, and aging/dementia, so it is not unique to ADHD.
  • Ex-Gaussian studies suggest ADHD-related variability is driven mainly by tau, the right-skewed tail of the reaction time distribution, consistent with occasional attentional lapses; standard deviation measures correlate strongly with mean reaction time (about 0.90), complicating interpretation, and one study reported a small fast-portion effect size of 0.08.
  • Stimulant medication attenuates or normalizes variability, especially tau and Fourier-based oscillation measures; faster stimulus event rates reduce ADHD-related variability, while reward/incentive effects are mixed, with some evidence that fast event rate plus reward may work synergistically. Neurophysiological accounts implicate frontal dysfunction, poor default-mode network suppression, and lower signal-to-noise ratios.

Methods

  • Narrative review of published cognitive, behavioral, neuroimaging, task-manipulation, and medication studies on reaction time variability in ADHD; no new participants or primary data are reported.
  • The main analysis is a qualitative synthesis across studies, with emphasis on ex-Gaussian and Fourier-transform metrics where available.

Limitations

  • Stated: conclusions are constrained by the wide range of variability measures used; most studies rely on reaction time standard deviation or coefficient of variation, which are too molar and confounded with mean reaction time, so component-specific metrics are needed.
  • Stated: few direct comparisons exist with other disorders showing high variability, few neuroimaging studies specifically examine variability in ADHD, findings for incentives and event rate are mixed, and it remains unclear whether variability is a cause or consequence.
  • Evident from the text: as a narrative review, it does not report a systematic search strategy, risk-of-bias assessment, or meta-analytic pooling.

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Integrity signals

Registry

Crossref · 10.1007/s13311-012-0138-5

Cites

96 of 114 references verified0 citation errors · 0 not checkable

Statistics

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Verification

Claims the paper makes

48 Not checked yet · 25 Own interpretation · 7 No basis given · 1 Supported · 1 Supported so far

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Show all 45 claims

  • Probably not a substantial claim. 7
  • It may state two separate claims as one. 33
37 of 37
  • The paper relies on this without support.

    Direct comparisons of reaction time variability between ADHD and other disorders with heightened reaction time variability are virtually nonexistent.

    “However, direct comparisons with other disorders with heightened reaction time variability are virtually nonexistent, despite their potential to inform our understanding of the phenomenon.”
  • The paper relies on this without support.

    The default mode network is a task-negative network that must be suppressed during task performance.

    “The DMN is considered a task negative network because it must be suppressed concomitant with activation in the task positive network (i.e., the neural network required to perform the cognitive task at hand).”
  • The paper relies on this without support.

    Long reaction times are the primary cause of reaction time variability in patients with ADHD.

    “which appears to be the primary cause of RTV for patients with ADHD.”
  • The paper relies on this without support.

    Neuroimaging research on reaction time variability in ADHD is much less common than in typically developing groups.

    “there are many fewer neuroimaging studies specifically investigating the phenomenon of RTV in ADHD.”
4 of 4

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Metadata

Authors
Tamm, L., Narad, M. E., Antonini, T. N., O'Brien, K. M., Hawk, L. W., & Epstein, J. N.
Affiliations
  • Cincinnati Children's Hospital Medical Center (US)
  • University at Buffalo, State University of New York (US)
Corresponding author
Tamm, Leanne
Venue
Neurotherapeutics
Publisher
Elsevier BV
Published
2012-07
Volume
9
Issue
3
Pages
500-508
ISSN
1878-7479 (ISSN-L)
OpenAlex
W2021199892
Cited by
324
References
114
Citations by year
2026: 22 · 2025: 12 · 2024: 18 · 2023: 28 · 2022: 29 · 2021: 35 · 2020: 25 · 2019: 27 · 2018: 25 · 2017: 20 · 2016: 27 · 2015: 20 · 2014: 24 · 2013: 11 · 2012: 1
FWCI
2.41
Type
journal article
Language
en
Open access
Locations
  • Neurotherapeutics (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
National Institute of Mental Health (K24MH064478)
Topics
  • Health Sciences › Medicine › Psychiatry and Mental health › Attention Deficit Hyperactivity Disorder
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Neural and Behavioral Psychology Studies
  • Social Sciences › Psychology › Neuropsychology and Physiological Psychology › Developmental and Educational Neuropsychology
Keywords
attention deficit hyperactivity disorder, reaction time variability, motivational incentives, attentional lapses, task-negative network, neurophysiological correlates, variability indices
MeSH terms
Attention Deficit Disorder with Hyperactivity, Humans, Inhibition, Psychological, Motivation, Neuropsychological Tests, Reaction Time

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