Response timing and interval estimation in ADHD

Beaumont, Stephen (1998) Response timing and interval estimation in ADHD. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Current theories of childhood ADHD stress motivational (Van der Meere, 1996), under arousal (Zentall & Zentall, 1993) or inhibitory difficulties (Barkley, 1997; Quay, 1988a, b). Also these children may exhibit an aversion to delay (Sonuga-Barke et al, 1992a, b and 1996). Underpinning all these approaches may be a difficulty with temporal estimation but little robust research has been carried out to test this hypothesis. This research was designed to test the ability of ADHD children to time responses and on an interval reproduction task.

21 ADHD children in middle childhood and 19 very young ADHD children were matched with controls (20 and 19 respectively). They were given a timing task and an interval reproduction task on a computer in baseline and contingency schedules. There were 30 trials for each task, alternating between trials for the older children and alternating blocks of 10 trials for the younger children. The timing trials required the older children to halt a caricature, after 7secs. on an ascending escalator over an arrow shown under the escalator. The interval reproduction task required the older children to estimate when the caricature had reached the arrow as the ascending caricature was obscured by a tunnel for the latter half of the ascent, giving an interval for reproduction of 3.5 seconds. The timing task for the younger children required them to drop toy bricks into a modified electric toy train as it passed under a central hopper feed, using a remote button, as it ran backwards and forwards along 165cm. of track. Optimum response time was app. 3 secs. In the interval reproduction task, the younger children were required to estimate when the train was under the hopper feed as a tunnel obscured a central section of track. The time for reproduction was approx. 1.5secs.

On the timing task, the older control group achieved performance close to ceiling, which gave them consistently higher hit scores. The performance of ADHD children was characterised by persistent premature responding especially in the contingency schedules. As a consequence of the control group performance these findings understate the difficulty that this task posed for the ADHD children.

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