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A research programme was undertaken to investigate the specific disabilities of hyperactive children and to evaluate the effectiveness of one of the stimulant drugs on the measures found to differentiate between hyperactives and normals. It is argued that a core group of symptoms involving inability to sustain attention and to control impulsivity can account for most of the deficits found in the hyperactive group. It also appears that the stimulants exert their main effect on these deficits. Correlational and factor analytic studies suggest that the same constellation of abilities underlies the behaviour of normal children in several areas of cognitive and social functioning.

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The usefulness of trontal lobe (FL) dysfunction as a conceptual model for Attention Deficit Hyperactivity Disorder (ADHD) was investigated.Twenty-four ADHD and 24 normal control (Ne) children were tested using tasks sensitive to FL deficits in motor control and problem solving skills and memory tasks sensitive to temporal lobe (TL) Venis Raymond for translatlng the abstract into French, and ta the many triends and colleagues who kept me going. l especially thank Ur. RichardVerbeek tar his on-going support and tolerance ot long hours and missed vacations.

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The effects of reward schedule (100%, 50%, and 30%) and termination of rewards (extinction) on 30 attention deficit disorder with hyperactivity (ADD-H) and 30 normal children were studied using measures of frustration (speed/strength of lever pulling) and attention (reaction time to a light signal). ADD-Hs pulled harder on the lever than controls during extinction and on the lowest (30%) partial schedule, providing empirical evidence that they respond with greater frustration than normals when expected rewards fail to appear. The groups did not differ on the attentional measure on 100% reward. However, the partial schedules appeared to have an alerting or motivating effect on the controls, so that they responded more quickly and consistently than ADD-Hs on the partial schedules. Findings are discussed with reference to opposing theories regarding the nature of the abnormal response of ADD-Hs to reward.

In this study, we examined heart rate and skin conductance levels of 18 children with attention-deficit hyperactivity disorder (ADHD) and 18 normal children as they performed a repetitive motor task during reward and extinction conditions. Fowles (1980, Psychophysiology, 17, 87-104; 1988, Psychophysiology, 25, 373-391) suggested that psychophysiological responsivity reflects activity in two of Gray's (1982, The neuropsychology of anxiety, Oxford University Press; 1987, The psychology of fear and stress, Cambridge University Press) motivational systems; heart rate reactivity during reward reflects activity in the behavioral activation system, and skin conductance reactivity during extinction reflects activity in the behavioral inhibition system. As predicted, control children showed increased heart rate when reward was present and increased skin conductance when reward was removed. Compared with controls, ADHD children failed to show increased skin conductance levels during extinction, suggesting a weak behavioral inhibition system. ADHD children also displayed faster heart rate habituation to reward.

The ability of the hyperactive child to maintain attention on three tasks was examined. One of the tasks, a Choice Reaction Time Task, measured attention for brief periods, while the other two measured sustained attention. Of the latter two, one was an experimenterpaced task(the Continuous Performance Test) and the other a self-paced task(the SeriaI Reaction Task) .It was found that the hyperactive children were no different from the normal controls in their ability to direct their attention for brief periods. They were however, significantly inferior to uhe controls in their ability to sustain attention, particularly on the experimenter-paced task. The effect of the stimulant drug methylphenidate was evaluated and found to be effective in improving performance on aIl three tests. Implications of these findings for the education of hyperactive children were discussed.