Behavioral and Brain Functions 2005, 1:12
doi:10.1186/1744-9081-1-12
Published 1 August 2005
Abstract (provisional)
http://www.behavioralandbrainfunctions.com/content/pdf/1744-9081-1-12.pdf
Background
The behaviour of children with Attention-Deficit / Hyperactivity
Disorder is often described as highly variable, in addition to being
hyperactive, impulsive and inattentive. One reason might be that they
do not acquire complete and functional sequences of behaviour, due to
inefficient reinforcement and extinction processes. The dynamic
developmental theory of ADHD proposes that these behavioural processes are inefficient because of hypofunctioning dopamine systems, resulting in a narrower time window for associating antecedent stimuli and
behaviour with its consequences. One effect of this may be that the
learning of behavioural sequences is delayed, and that only short
behavioural sequences are acquired in ADHD, ultimately leading to
deficient development of verbally governed behaviour and self control.
The present study investigated acquisition of response sequences in the
behaviour of children with ADHD.
Methods
Fifteen boys with ADHD and thirteen boys without, all aged between 6-9
yr, completed a computerized task presented as a game with two squares
on the screen. One square was associated with reinforcement. The task
required responses by the computer mouse under reinforcement contingencies of variable interval schedules. Reinforcers were cartoon
pictures and small trinkets. Measures related to response location
(spatial dimension) and to response timing (temporal dimension) were
analyzed by autocorrelations of consecutive responses across five lags.
Acquired response sequences were defined as predictable responding
shown by high explained variance.
Results
Children with ADHD acquired shorter response sequences than comparison children on the measures related to response location. None of the groups showed any predictability in response timing. Response
sequencing on the measure related to the discriminative stimulus was highly related to parent scores on a rating scale for ADHD symptoms.
Conclusions
The findings suggest that children with ADHD have problems with
learning long sequences of behaviour, particularly related to response location, purportedly due to a narrower time window available for reinforcers to work effectively. The study represents a new approach to analyzing the moment-to-moment dynamics of behaviour, and provides support for the theory that reinforcement processes are altered in ADHD.