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.

Objective The purpose of the research study was to examine the manifestation of variability in reaction times (RT) in children with Attention Deficit Hyperactivity Disorder (ADHD) and to examine whether RT variability presented differently across a variety of neuropsychological tasks, was present across the two most common ADHD subtypes, and whether it was affected by reward and event rate (ER) manipulations. Method Children with ADHD-Combined Type (n=51), ADHD-Predominantly Inattentive Type (n=53) and 47 controls completed five neuropsychological tasks (Choice Discrimination Task, Child Attentional Network Task, Go/No-Go task, Stop Signal Task, and N-back task), each allowing trial-by-trial assessment of reaction times. Multiple indicators of RT variability including RT standard deviation, coefficient of variation and ex-Gaussian tau were used. Results Children with ADHD demonstrated greater RT variability than controls across all five tasks as measured by the ex-Gaussian indicator tau. There were minimal differences in RT variability across the ADHD subtypes. Children with ADHD also had poorer task accuracy than controls across all tasks except the Choice Discrimination task. Although ER and reward manipulations did affect children’s RT variability and task accuracy, these manipulations largely did not differentially affect children with ADHD compared to controls. RT variability and task accuracy were highly correlated across tasks. Removing variance attributable to RT variability from task accuracy did not appreciably affect between-group differences in task accuracy. Conclusions High RT variability is a ubiquitous and robust phenomenon in children with ADHD.

Parent-teacher agreement on Attention Deficit/Hyperactivity Disorder (ADHD) symptom ratings range from low to moderate. Most studies evaluating parent-teacher agreement have not assessed measurement invariance across raters. Hence, it is unclear whether discordance across raters is due to differing ADHD constructs across raters or other factors (e.g., subjective differences across raters). Additionally, the effect of development on parent-teacher agreement is relatively unknown. To address these limitations, the present study utilized parent and teacher ADHD ratings from a large (N=6,659), developmentally diverse (ages 4–17) sample. Exploratory structural equation modeling using half the sample and then Confirmatory Factor Analysis (CFA) on the second half of the sample identified a two-factor structure for the 18 ADHD symptoms. CFA invariance analyses demonstrated that the two factor symptom structure was similar across raters and age groups. Also, parents reported greater severity of ADHD symptoms than teachers and both parents and teachers report higher levels of HI in younger children than older children and consistent levels of inattention across development. Finally, correlations between parent-teacher ratings of like-factor ratings were weak for Inattention (IA) and moderate-strong for Hyperactivity/Impulsivity (HI) and that the magnitude of parent-teacher agreement did not vary across development. In conclusion, while parent and teacher ratings of ADHD behaviors are only weakly to moderately correlated, each reporter provides unique and valid clinical information as it relates to ADHD symptom presentation.

This study examined the effects of methylphenidate (MPH) on reaction time (RT) variability in children with Attention Deficit Hyperactivity Disorder (ADHD). Using a broad battery of computerized tasks and both conventional and ex-Gaussian indicators of RT variability, in addition to within-task manipulations of Incentive and Event Rate (ER), this study comprehensively examined the breadth, specificity, and possible moderators of MPH effects on RT variability. Ninety-three children with ADHD completed a four-week within subject, randomized, double-blind, placebo-controlled crossover trial of MPH to identify an optimal dosage. Children were then randomly assigned to receive either their optimal MPH dose or placebo after which they completed five neuropsychological tasks, each allowing trial-by-trial assessment of reaction times (RT). Stimulant effects on RT variability were observed on both measures of the total RT distribution (i.e., coefficient of variation) as well as on an ex-Gaussian measure examining the exponential portion of the RT distribution (i.e., tau). There was minimal, if any, effect of MPH on performance accuracy or RT speed. Within-task Incentive and ER manipulations did not appreciably affect stimulant effects across the tasks. The pattern of significant and pervasive MPH effects on RT variability and few MPH effects on accuracy and RT speed suggest that MPH primarily affects RT variability. Given the magnitude and breadth of MPH effects on RT variability as well as the apparent specificity of these MPH effects to RT variability indicators, future research should focus on neurophysiological correlates of MPH effects on RT variability in an effort to better define MPH pharmacodynamics.

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Importance This study extends the literature regarding Attention-Deficit/Hyperactivity Disorder (ADHD) related driving impairments to a newly-licensed, adolescent population. Objective To investigate the combined risks of adolescence, ADHD, and distracted driving (cell phone conversation and text messaging) on driving performance. Design Adolescents with and without ADHD engaged in a simulated drive under three conditions (no distraction, cell phone conversation, texting). During each condition, one unexpected event (e.g., car suddenly merging into driver's lane) was introduced. Setting Driving simulator. Participants Adolescents aged 16–17 with ADHD (n=28) and controls (n=33). Interventions/Main Exposures Cell phone conversation, texting, and no distraction while driving. Outcome Measures Self-report of driving history; Average speed, standard deviation of speed, standard deviation of lateral position, braking reaction time during driving simulation. Results Adolescents with ADHD reported fewer months of driving experience and a higher proportion of driving violations than controls. After controlling for months of driving history, adolescents with ADHD demonstrated more variability in speed and lane position than controls. There were no group differences for braking reaction time. Further, texting negatively impacted the driving performance of all participants as evidenced by increased variability in speed and lane position. Conclusions This study, one of the first to investigate distracted driving in adolescents with ADHD, adds to a growing body of literature documenting that individuals with ADHD are at increased risk for negative driving outcomes. Furthermore, texting significantly impairs the driving performance of all adolescents and increases existing driving-related impairment in adolescents with ADHD, highlighting the need for education and enforcement of regulations against texting for this age group.

Background and purpose This study examines attention, processing speed, and executive functioning in pediatric brain tumor survivors treated with proton beam radiation therapy (PBRT). Material and methods We examined 39 survivors (age 6–19 years) who were 3.61 years post-PBRT on average. Craniospinal (CSI; n = 21) and focal (n = 18) subgroups were analyzed. Attention, processing speed, and executive functioning scores were compared to population norms, and clinical/demographic risk factors were examined. Results As a group, survivors treated with focal PBRT exhibited attention, processing speed, and executive functioning that did not differ from population norms (all p > 0.05). Performance in the CSI group across attention scales was normative (all p > 0.05), but areas of relative weakness were identified on one executive functioning subtest and several processing speed subtests (all p < 0.01). Conclusions Survivors treated with PBRT may exhibit relative resilience in cognitive domains traditionally associated with radiation late effects. Attention, processing speed, and executive functioning remained intact and within normal limits for survivors treated with focal PBRT. Among survivors treated with CSI, a score pattern emerged that was suggestive of difficulties in underlying component skills (i.e., processing speed) rather than true executive dysfunction. No evidence of profound cognitive impairment was found in either group.

Objective Sluggish cognitive tempo (SCT) symptoms are associated with social difficulties in children, though findings are mixed and many studies have used global measures of social impairment. The present study tested the hypothesis that SCT would be uniquely associated with aspects of social functioning characterized by withdrawal and isolation, whereas attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) symptoms would be uniquely associated with aspects of social functioning characterized by inappropriate responding in social situations and active peer exclusion. Method Participants were 158 children (70% boys) between ages 7–12 years being evaluated for possible ADHD. Both parents and teachers completed measures of SCT, ADHD, ODD, and internalizing (anxiety/depression) symptoms. Parents also completed ratings of social engagement and self-control. Teachers also completed measures assessing asociality and exclusion, as well as peer ignoring and dislike. Results In regression analyses controlling for demographic characteristics and other psychopathology symptoms, parent-reported SCT symptoms were significantly associated with lower social engagement (e.g., starting conversations, joining activities). Teacher-reported SCT symptoms were significantly associated with greater asociality/withdrawal and ratings of more frequent ignoring by peers, as well as greater exclusion. ODD symptoms and ADHD hyperactive-impulsive symptoms were more consistently associated with other aspects of social behavior, including peer exclusion, being disliked by peers, and poorer self-control during social situations. Conclusions Findings provide the clearest evidence to date that the social difficulties associated with SCT are primarily due to withdrawal, isolation, and low initiative in social situations. Social skills training interventions may be effective for children displaying elevated SCT symptomatology.