In order to classify attention-deficit-hyperactivity disorder (ADHD) in Ii-
year-old children, the role of specific attentional and motor deficits was
examined. Participants comprised 22 children with ADHD (19 male, 3 female;
median age 11 years, range 8.8 to 13.5 years) and 20 control children (17 m
ale, 3 female; median age 10.6 years, range 8.2 to 12.6 years). Neuromotor
assessment indicated that while both groups needed more time to complete fi
nger compared to hand movements, this increase was more pronounced in child
ren with ADHD. Reaction-time testing with continuous-force recording identi
fied both motor and attentional deficits in children with ADHD. Longer inte
rvals between force onset and force peak, and higher rate of responses with
multiple force peaks (particularly in the bilateral condition) revealed sp
ecific deficits in the speed and quality of their motor output. Increase in
errors and variability of force onsets indicated attentional deficits. Pre
diction analysis indicated that force-onset variability contributed signifi
cantly to group classification which was 85.7% correct. Neither neuromotor
assessment nor specific motor deficits contributed significantly to classif
ication, indicating that pure motor-speed measures play a minor role in cha
racterizing ADHD in this age range.