On the basis of Gray's theory, Quay suggested that conduct
disorder
(CD) is associated with
a Behavioural Activation System (BAS) that dominates over the Behavioural
Inhibition
System (BIS), whereas attention deficit hyperactivity disorder (ADHD)
is characterised by
an underactive BIS. Two studies were conducted to test the hypothesis that
the dominance
of the BAS over the BIS is more pronounced in CD comorbid with ADHD (CD/ADHD)
than in CD alone. First of all, a response perseveration task was used,
i.e. the door-opening
task (Daugherty & Quay, 1991). In this game, the subject chooses either
to open the next
door or to stop playing; there is a steadily increasing ratio of punished
responses to rewarded
responses and a large number of doors opened is indicative of response
perseveration. As
expected, a steady increase in the number of doors opened was found across
normal control
(NC) boys, CD boys, and CD/ADHD boys (NC<CD<CD/ADHD). Second,
the
dominance of the BAS over the BIS was examined by observing the social
behaviour of the
child in interaction with a research assistant who alternately activated
the BAS and the BIS
while a game was played. The behaviour of the children was analysed according
to
ethological methods. Group differences in the frequencies of three out
of five behavioural
categories were in line with the results of the door-opening task (NC<CD<CD/ADHD).