The effect of enhanced motivation on time reproduction abilities in children with ADHD
Date
2001
Authors
McInerney, Robert John
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Abstract
Research has shown that chrildren with attention deficit/hyperactivity disorder (ADHD) demonstrate poor performance on time reproduction paradigms and related measures that assess one's sense of time. In Barkley's (1997) model of ADHD, a central deficit in behavioural inhibition is hypothesized to set the occasion for impairments in four subservient executive functions. One of these executive functions, spatial working memory, is hypothesized in turn to underlie a number of complex abilities including one's subjective sense of time. Motivational factors, however, may also impact performance on time reproduction paradigms as these tasks are frequently long and offer no feedback and li1tle inherent reward.
The primary goal of this study was to examine whether children with ADHD have a true deficit in subjective sense of time, or whether their impairment instead reflects a motivational deficit. To rest this possibility, 60 children (30 children with ADHD and 30 controls matched by age and gender) between the age of 6 and 13 years completed two versions of a time reproduction paradigm, along with measures of working memory and a measure of behavioural inhibition. On one time reproduction task (the "'regular version"), subjects saw a light bulb appear on a computer monitor for a duration that ranged between 3 and 17 seconds, and had to reproduce the duration by turning their own computer-based light bulb on and off for the same amount of time as the computer generated target duration. The second version of the paradigm (the "enhanced" version) was similar to the first, except that following each trial subjects received feedback that consisted of a sham score, reinforcing graphics, and a verbal accolade, which collectively indicated they had done well on their time reproductions. On the enhanced version, subjects were told that if they did "well enough'' and attained a high score, they would be able to choose a prize from a large, attractively-wrapped gift box. They were instructed further that if they did not score as highly, they could still choose a prize, but only from the much smaller prize box, wrapped in white fined writing paper.
Conditions were counterbalanced for presentation and in truth, all children received identical sham feedback so that at the end of the game, all participants "won" the bigger prize. It was hypothesized that if a motivational deficit underlies the poor time reproduction abilities observed in children with ADHD, the deficit might be ameliorated by the increased motivation provided by the enhanced version of the task.
Results indicated that children with ADHD made significantly fewer errors in the enhanced versus the regular condition of the time reproduction paradigm. In contrast, control subjects exhibited no reliable change in performance between versions of the task. Despite the improvement shown by children with ADHD, they continued to perform significantly below controls even on the enhanced version of the game. The groups also differed significantly on the measures of working memory and behavioural inhibition.
The impact of self-reported motivation, working memory, and behavioural inhibition on time reproduction, and the relevance of these results in context of Barkley's theory of ADHD are examined and discussed.