Reaction time distribution analysis of spatial correspondence effects

Since 1994, group reaction time (RT) distribution analyses of spatial correspondence effects have been used to evaluate the dynamics of the spatial Simon effect, a benefit of correspondence of stimulus location information with response location for tasks in which stimulus location is irrelevant. We review the history and justification for analyzing group RT distributions and clarify which conditions result in the Simon effect decreasing across the distribution and which lead to flat or increasing functions. Although the standard left-right Simon effect typically yields a function for which the effect decreases as RT increases, in most other task variations, the Simon effect remains stable or increases across the RT distribution. Studies that have used other means of evaluating the temporal dynamics of the Simon effect provide converging evidence that the changes in the Simon effect across the distribution are due mainly to temporal activation properties, an issue that has been a matter of some dispute.     

Screening for ADHD in an adult social phobia sample

Objective: Recent studies have suggested a link between a primary anxiety disorder and ADHD. Method: A total of 39 participants with a primary diagnosis of social phobia were compared with 178 patients with ADHD and 88 patients with other psychiatric disorders on measures for childhood and adult ADHD (the Wender Utah Rating Scale and the Adult ADHD Self-Report Scale). Results: Childhood symptoms of ADHD were reported by 7.8% of the social phobia participants, and 5.1% scored within the range of adult ADHD. The social phobia group reported significantly fewer ADHD symptoms than both of the comparison groups, who frequently reported social anxiety. Conclusion: Participants with social phobia recruited from the general population are less likely to suffer from ADHD. In contrast, patients with ADHD and patients with other psychiatric disorders appear to be likely to suffer from social anxiety.     

Reaction Time Distribution Analysis of Neuropsychological Performance in an ADHD Sample

Differences in reaction time (RT) variability have been documented between children with and without Attention Deficit Hyperactivity Disorder (ADHD). Most previous research has utilized estimates of normal distributions to examine variability. Using a nontraditional approach, the present study evaluated RT distributions on the Conners’ Continuous Performance Test in children and adolescents from the Multimodal Treatment Study of ADHD sample compared to a matched sample of normal controls (n = 65 pairs). The ex-Gaussian curve was used to model RT and RT variability. Children with ADHD demonstrated faster RT associated with the normal portion of the curve and a greater proportion of abnormally slow responses associated with the exponential portion of the curve. These results contradict previous interpretation that children with ADHD have slower than normal responding and demonstrate why slower RT is found when estimates of variability assume normal Gaussian distributions. Further, results of this study suggest that the greater number of abnormally long RTs of children with ADHD reflect attentional lapses on some but not all trials.     

Short report: Reaction time analysis with outlier exclusion: Bias varies with sample size

To remove the influence of spuriously long response times, many investigators compute “restricted means”, obtained by throwing out any response time more than 2.0, 2.5, or 3.0 standard deviations from the overall sample average. Because reaction time distributions are skewed, however, the computation of restricted means introduces a bias: the restricted mean underestimates the true average of the population of response times. This problem may be very serious when investigators compare restricted means across conditions with different numbers of observations, because the bias increases with sample size. Simulations show that there is substantial differential bias when comparing conditions with fewer than 10 observations against conditions with more than 20. With strongly skewed distributions and a cutoff of 3.0 standard deviations, differential bias can influence comparisons of conditions with even more observations.     

A controlled clinical comparison of attention performance in children with ADHD in a virtual reality classroom compared to standard neuropsychological methods.

In this initial pilot study, a controlled clinical comparison was made of attention perforance in children with attention deficit-hyperactivity disorder (ADHD) in a virtual reality (VR) classroom. Ten boys diagnosed with ADHD and ten normal control boys participated in the study. Groups did not significantly differ in mean age, grade level, ethnicity, or handedness. No participants reported simulator sickness following VR exposure. Children with ADHD exhibited more omission errors, commission errors, and overall body movement than normal control children in the VR classroom. Children with ADHD were more impacted by distraction in the VR classroom. VR classroom measures were correlated with traditional ADHD assessment tools and the flatscreen CPT. Of note, the small sample size incorporated in each group and higher WISC-III scores of normal controls might have some bearing on the overall interpretation of results. These data suggested that the Virtual Classroom had good potential for controlled performance assessment within an ecologically valid environment and appeared to parse out significant effects due to the presence of distraction stimuli.     

Sleep disturbance and neuropsychological function in young children with ADHD

Sleep disturbance, common among children with ADHD, can contribute to cognitive and behavioral dysfunction. It is therefore challenging to determine whether neurobehavioral dysfunction should be attributed to ADHD symptoms, sleep disturbance, or both. The present study examined parent-reported sleep problems (Children’s Sleep Habits Questionnaire) and their relationship to neuropsychological function in 64 children, aged 4–7 years, with and without ADHD. Compared to typically developing controls, children with ADHD were reported by parents to have significantly greater sleep disturbance—including sleep onset delay, sleep anxiety, night awakenings, and daytime sleepiness—(all p ≤ .01), and significantly poorer performance on tasks of attention, executive control, processing speed, and working memory (all p < .01). Within the ADHD group, total parent-reported sleep disturbance was significantly associated with deficits in attention and executive control skills (all p ≤ .01); however, significant group differences (relative to controls) on these measures remained (p < .01) even after controlling for total sleep disturbance. While sleep problems are common among young children with ADHD, these findings suggest that inattention and executive dysfunction appear to be attributable to symptoms of ADHD rather than to sleep disturbance. The relationships among sleep, ADHD symptoms, and neurobehavioral function in older children may show different patterns as a function of the chronicity of disordered sleep.     

A critical appraisal of the role of neuropsychological deficits in preschool ADHD

The present study aimed at improving our understanding of the role of neuropsychological deficits in preschool Attention Deficit Hyperactivity Disorder (ADHD). The study included 52 children in the ADHD group and 72 controls (age 4–6 years). Both laboratory measures and teacher reports of executive deficits (i.e., working memory, inhibition, and shifting), delay-related behaviors (i.e., the preference for minimizing delay), and emotional functions (i.e., emotion recognition and regulation) were included. Variable-oriented analyses were complemented with person-oriented analyses (i.e., identifying the proportion of patients considered impaired). Results showed that the ADHD group differed from controls with regard to all measures of executive functioning and most measures of delay-related behaviors, but few differences were found for emotional functioning. A substantial subgroup (23%) of children with ADHD did not have a neuropsychological deficit in any domain. There were subgroups with executive or delay-related deficits only, but no pure emotional subgroup. The overlap between different neuropsychological deficits was much larger when teacher reports were used as opposed to laboratory measures. Regarding functional impairments, large mean differences were found between the ADHD group and controls. However, neuropsychological deficits were not able to explain individual variations in daily life functioning among children with ADHD. In conclusion, the present study identified some important methodological and theoretical issues regarding the role of neuropsychological functioning in preschool ADHD.     

A review of adult ADHD: a neuropsychological and neuroimaging perspective

Attention-deficit/hyperactivity disorder (ADHD) is a developmental disorder which effects an estimated 3% to 5% of children. Despite estimates that ADHD persists in 30% to 70% of adults having had the disorder in childhood, ADHD in adulthood remains controversial. This report summarizes current thinking in the diagnosis and etiology of adult ADHD. Most theories posit that ADHD is related to anomalies in frontal lobe function and dopaminergic transmission. However, there is debate as to whether ADHD is a unitary disorder with different manifestations, a syndrome, or multiple disorders. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, classifies ADHD into inattention, hyperactivity-impulsivity, and combined subtypes. Although problems with cognition are core ADHD symptoms, self-reporting has not been a reliable predictor of neuropsychological test performance. Nevertheless, we suggest that a performance-based diagnosis, including empirically derived, age-sensitive neuropsychological tests, provides the best hope of dissociating ADHD from psychiatric disorders with similar symptoms. We also describe the promise of new neuroimaging technologies, such as functional magnetic resonance imaging, in elucidating the pathophysiology of ADHD and similar psychiatric disorders.     

Event rate and reaction time performance in ADHD: Testing predictions from the state regulation deficit hypothesis using an ex-Gaussian model

According to the state regulation deficit (SRD) account, ADHD is associated with a problem using effort to maintain an optimal activation state under demanding task settings such as very fast or very slow event rates. This leads to a prediction of disrupted performance at event rate extremes reflected in higher Gaussian response variability that is a putative marker of activation during motor preparation. In the current study, we tested this hypothesis using ex-Gaussian modeling, which distinguishes Gaussian from non-Gaussian variability. Twenty-five children with ADHD and 29 typically developing controls performed a simple Go/No-Go task under four different event-rate conditions. There was an accentuated quadratic relationship between event rate and Gaussian variability in the ADHD group compared to the controls. The children with ADHD had greater Gaussian variability at very fast and very slow event rates but not at moderate event rates. The results provide evidence for the SRD account of ADHD. However, given that this effect did not explain all group differences (some of which were independent of event rate) other cognitive and/or motivational processes are also likely implicated in ADHD performance deficits.     

An investigation into the relationship among ADHD symptomatology, creativity, and neuropsychological functioning in children.

This paper examined the relationship between creativity and ADHD symptomatology. First, the presence of ADHD symptomatology within a creative sample was explored. Secondly, the relationship between cognitive functioning and ADHD symptomatology was examined by comparing four groups, aged 10-12 years: 1) 29 ADHD children without creativity, 2) 12 creative children with ADHD symptomatology, 3) 18 creative children without ADHD symptomatology, and 4) 30 controls. Creativity, intelligence, processing speed, reaction time, working memory, and inhibitory control were measured. Results showed that 40% of the creative children displayed clinically elevated levels of ADHD symptomatology, but none met full criteria for ADHD. With regard to cognitive functioning, both ADHD and creative children with ADHD symptoms had deficits in naming speed, processing speed, and reaction time. For all other cognitive measures the creative group with ADHD symptoms outperformed the ADHD group. These findings have implications for the development and management of creative children.     

Impact of comorbid depressive symptoms on neuropsychological performance in obsessive-compulsive disorder.

There is indirect evidence from previous research that several executive disturbances in obsessive-compulsive disorder (OCD) are mediated by comorbid depressive symptoms. For the present study, the authors investigated whether OCD patients with elevated Hamilton Rating Scale for Depression (HRSD) scores would exhibit deficits in tasks sensitive to the medial and dorsolateral frontal cortex as well as other executive tasks. The 36 OCD patients were split along the median according to their HRSD scores and compared with matched control subjects. Patients with high HRSD scores performed significantly worse than control subjects and patients with low HRSD scores on the Wisconsin Card Sorting Test, the Trail-Making Test (TMT, Part B), and the TMT difference score. Moreover, patients with high HRSD scores exhibited deficits on a (creative) verbal fluency task. It is suggested that comorbid depressive symptoms may have artificially inflated some executive deficit scores in previous studies.