Exploring the Variability in Reaction Times of Preschoolers at Risk of Attention-Deficit/Hyperactivity Disorder: an ex-Gaussian Analysis
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Reaction times (RTs) are typically slower and more variable in individuals with attention-deficit/hyperactivity disorder (ADHD). Analysis of the ex-Gaussian RT distribution, which is described by mu, sigma (mean and standard deviation, respectively, of the normal distribution) and tau (that of exponential distribution), reveals that individuals with ADHD do not display overall slower RTs but have a high proportion of extremely slow RTs, represented by a high tau value. Although this is a vital component for describing ADHD-related RT variability in school-aged children, adolescents, and adults, it has not been thoroughly studied at the preschool age. We assessed 65 preschoolers at risk of ADHD and 98 typically developing preschoolers with the Conners’ Kiddie Continuous Performance Test (K-CPT) and parental and teacher reports of ADHD symptoms. We found that preschoolers at risk of ADHD had greater values for RT standard deviation, sigma, and tau than typically developing preschoolers at long inter-stimulus intervals (ISIs) (3 s), but not at short ISIs (1.5 s). This suggests that attention problems in preschool children may only be apparent in the tasks with a relatively slow event rate. Our study demonstrates that the ex-Gaussian tau value is essential for describing the inattentive component of task performance in preschoolers with heightened ADHD symptoms. Furthermore, the fact that the tau effect was modulated by ISI suggests that the longer duration (3 s vs. 1.5 s) is a non-optimal energetic state in preschoolers at risk of ADHD, and that this might account for the subtle attentional flaw in task performance.
KeywordsADHD Reaction time Preschool children Ex-Gaussian
This study was supported by grants from the Ministry of Science and Technology (MOST 103-2410-H-182-003-MY3), and Chang Gung University (NMRPD1D0131, NMRPD1D0132, NMRPD1D0133), Taiwan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors would like to express our thanks to all the participants and their parents and our research assistants for their contribution to this study.
Compliance with Ethical Standards
Conflict of Interest
The authors have declared that they have no competing conflicts of interest.
All procedures involving human participants were in accordance with the ethical standards of the institutional and national research committees, the 1964 Helsinki Declaration, and its later amendments, or comparable ethical standards.
This study was approved by the Research Ethics Committee of the National Taiwan University Hospital and by the Chang Gung Medical Foundation Institutional Review Board, and parents’ written informed consent and child assent were obtained before study implementation.
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