Biomedical subjects
Publications and source records attributed to J van der Meere.
Motor presetting was investigated in hyperactive children, learning disabled children and normal controls. The reaction time of the hyperactive group was more sensitive to increases in interstimulus interval (event rate) than was that of the learning disabled and the controls. This finding indicates that hyperactive children have difficulty with motor presetting.
A sustained attention deficit implies a deficit originating in the course of a task. A series of studies previously indicated that task inefficiency in hyperactive children is independent of task duration. The present study shows that differences in body activity between hyperactive and control children are also independent of task duration. However, the groups did differ in visual behaviour, i.e. hyperactive children did look away from the task more frequently as time proceeds. This visual behaviour did not interfere with task accuracy. It is argued that the results indicate that hyperactive children may have prevented a further deterioration of task efficiency over time through self stimulation.
A sustained attention deficit is defined as a significant decrement in task performance with task duration (time-on-task). Time-on-task effects are reported using a self-paced paper and pencil cancellation test (PPCT) in normals and in subgroups of pervasively hyperactive children. The hyperactive subgroups were pervasively hyperactive both at home and at school. They differed in degree of pervasiveness in three laboratory conditions. Task inefficiency was most pronounced in the most pervasively hyperactive group. There was no evidence in favour of a sustained attention deficit in hyperactivity: no differences were found in decline in task efficiency between the controls and the subgroups of hyperactive children.
A review is made of available studies using the Additive Factor Method (AFM) in clinical research. The paper argues that by using the AFM in studies of psychological dysfunctioning a major contribution can be made: first, in preventing spurious findings, second, distinguishing between group differences with and without information processing deficits, and third, by identifying fundamental processes which may be impaired. This may offer psychodiagnostics an empirical basis on which to define disorders. This paper reviews studies contributing to this endeavour. It further raises the question of how to interpret clinical research, which is conducted in the tradition of information processing but not within the frame of reference of the AFM. It is suggested that such research is useful and complementary to that conducted using the AFM. Further, it is suggested that the role of energetical factors in clinical disorders and in their treatment is an important area for future experimental clinical research.
The Additive Factor Method assumes that task performance is the sum of sequential and independent processes. We studied the duration of the central processes (memory search and decision) and the motor decision process in hyperactive and learning-disabled children under so-called divided attention and S-R compatibility conditions. It was found that the learning-disabled were impaired in memory search and decision processes whereas hyperactives were impaired in the motor decision process.
This experiment was designed to investigate the hypothesized distractibility of hyperactive children in a focused attention task. Distractibility was defined in terms of Shiffrin and Schneider's model of focused attention as the ability to ignore irrelevant in favor of relevant information. Failure to inhibit processing of irrelevant information indicates a focused attention deficit. Task efficiency in all children decreased when irrelevant information was presented. The mean reaction time, within-subject variance of reaction time, and error percentage all increased compared with a nondistraction condition. Thus, the demands of focused attention, as formulated in the model, were measured optimally. Since hyperactives and controls did not differ significantly with respect to task efficiency in the distraction condition, a focused attention deficit in hyperactives was not demonstrated. The hyperactives did nevertheless make more errors and their responding was more variable than the controls. However, the difference in error percentages between hyperactives and controls was associated with the difference in IQ. It is speculated that the variable responding in hyperactives is caused by a less optimal state of performance unrelated to distractibility.
This paper reviews the concept of sustained attention, placing it within a theoretical framework in which deficits of attention are conceived of as deficits of controlled information processing. Two types of deficit of sustained attention are distinguished: perceptual sensitivity and perceptual criterion. These two deficits are linked to a model of human performance that links controlled processes to the energetic pools: arousal and activation. Perceptual sensitivity (d') deficits are said to reflect arousal deficiencies, especially when observed in the early period of a vigil. Perceptual criterion deficits are associated with the activation pool and the response criterion measure beta. Despite clear evidence of perceptual deficiency in the hyperactive children to a greater extent than in the control group, and that performance in d' declined with time on task, a significant interaction failed to occur between group classification and time on task. Thus, the results failed to support the hypothesis of a sustained attention deficit in hyperactives, since if hyperactives have a sustained attention deficit, both d' and beta should have shown a significantly greater decline in the hyperactive group than in the controls with time on task.
Children with a diagnosis of attention deficit disorder with hyperactivity can correct errors, just as controls can. They differ from controls in how they adjust the speed of processing on a trial after they have committed an error. Controls are fast in responding after an error when cognitive load is small. When cognitive load is high, however, they take considerable time to ensure, after an error has occurred, that a correct response is given. After an error has been committed, hyperactive children, irrespective of the demands of load, have no response adjustment and maintain a constant rate of processing.
The hypothesis that pervasively hyperactive children have disturbed attention and fail to acquire learning skills is tested. Attention and learning skills are defined here in terms of the controlled versus automatic processing distinction. In this report 12 pervasively hyperactive children and 12 controls were compared for their ability to develop automatic information processing during a memory recognition task. It was predicted that, if hyperactive children failed to adopt task-appropriate cognitive sets, automatic processing would either fail or develop more slowly than in controls. The data indicated that the groups differed in task efficiency: hyperactive children were slower, within-subject variance of reaction time was greater, and errors occurred more frequently than in controls. However, group differences could not be explained in terms of an attention dysfunction or an inability to develop automatic processing in the hyperactive child.
Task performance of 12 pervasive hyperactives and controls was studied in a divided attention reaction time experiment. The two groups differed with respect to task efficiency. The hyperactives were slower than controls, had more variable reaction times, and made more frequent errors. Task inefficiency could not be explained by a deficiency in divided attention or impulsive responding in the hyperactive group. Further, the observed differences in IQ between the groups could not account for the differential performance finding. It is concluded that input and/or output processes, probably in combination with energetical factors, might be disturbed in hyperactive children.