Abstract
Dysfunctions in perceptual timing have been reported in children with ADHD, but so far only from studies that have not used the whole set of timing paradigms available from the literature, with the diversity of findings complicating the development of a unified model of timing dysfunctions and its determinants in ADHD. Therefore, we employed a comprehensive set of paradigms (time discrimination, time estimation, time production, and time reproduction) in order to explore the perceptual timing deficit profile in our ADHD sample. Moreover, we aimed to detect predictors responsible for timing task performance deficits in children with ADHD and how the timing deficits might be positively affected by methylphenidate. Male children with ADHD and healthy control children, all aged between 8 and 13 years, participated in this longitudinal study with three experimental sessions, where children with ADHD were medicated with methylphenidate at the second session but discontinued their medication at the remaining sessions. The results of our study reveal that children with ADHD were impaired in all timing tasks, arguing for a general perceptual timing deficit in ADHD. In doing so, our predictor analyses support the notion that distinct but partially overlapping cognitive mechanisms might exist for discriminating, estimating/producing, and reproducing time intervals. In this sense, working memory deficits in terms of an abnormally fast internal counting process might be common to dysfunctions in the time estimation/time production tasks and in the time reproduction task, with attention deficits (e.g., in terms of disruptions of the counting process) additionally contributing to time estimation/time production deficits and motivational alterations additionally contributing to time reproduction deficits. Methylphenidate did not significantly alter performance of the ADHD sample, presumably due to limited statistical power of our study. The findings of our study demonstrate a pivotal role of disturbed working memory processes in perceptual timing task performance in childhood ADHD, at the same time broadening the view for additional attentional and motivational determinants of impaired task performance.
Highlights
Time exists from the beginning of each individual’s life
As correlations have been found between time estimation and time reproduction tasks in other studies (Bauermeister et al, 2005), not consistently (Smith et al, 2002) or not adjusted for multiple comparisons (Hurks and Hendriksen, 2011), and interval underreproduction is prominent in children and adolescents with attention-deficit/hyperactivity disorder (ADHD) as well (Kerns et al, 2001; McInerney and Kerns, 2003), abnormally fast counting processes might be a prerequisite for time reproduction deficits in children with ADHD as well, a lack of association between both tasks in our study suggests that different mechanisms might still be more important
Children with ADHD seem to suffer from a general perceptual timing deficit which is not restricted to specific timing tasks
Summary
Time exists from the beginning of each individual’s life. Starting during intrauterine life, the unborn child is exposed to external time cues like the mothers’ sleep-wake-cycle, feeding times, or sounds. As one gets older, synchronizing activities and keeping deadlines and appointments becomes more and more important, and the extent to which the individual is able to cope with these demands decides to which extent he or she meets performance or social requirements. In addition to these cognitive-structural aspects of timing, the perception of time can be influenced by our emotions: We wish to escape from certain situations that we perceive as boring and neverending, but on the other hand, time is running out when we are engaged in activities that give us pleasure. Time is a static external framework, but is subject to variability of individual perception
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