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J Sergeant

Publications and source records attributed to J Sergeant.

13 recordsLinked to original sources
PubMed1992

Event-related desynchronization: the effects of energetic and computational demands.

The effects of a subject's activation state on cognitive processing were studied, while subjects performed verbal and non-verbal tasks under a speed and accuracy instruction. It was found that stressing speed influenced the level of prestimulus alpha power and consequently the amount of relative event-related desynchronization (ERD). Increasing task complexity led to an increase in the amount and duration of relative ERD. Both prestimulus level of alpha power and relative ERD were asymmetrically distributed over the left and right hemispheres. No verbal/non-verbal task-dependent asymmetries in phasic ERD were found. The data suggest that the level of prestimulus alpha power is mainly influenced by the subject's activation state, whereas relative ERD mainly reflects phasic changes in cognitive processing.

Adult↗
PubMed1992

A motor presetting study in hyperactive, learning disabled and control children.

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.

Aptitude↗
PubMed1991

Sustained attention and pervasive hyperactivity.

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.

Attention↗
PubMed1990

Additive factor method applied to psychopathology with special reference to childhood hyperactivity.

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.

Arousal↗
PubMed1989

The additive factor method: a differential diagnostic tool in hyperactivity and learning disability.

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.

Attention↗
PubMed1988

Focused attention in pervasively hyperactive children.

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.

Attention↗
PubMed1988

Controlled processing and vigilance in hyperactivity: time will tell.

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.

Attention↗
PubMed1988

The use of bilateral skin conductance measurement in elucidating stimulus versus response processing influences on the orienting reaction.

In three experiments the importance of behavioural consequences as a determinant of the amplitude of the electrodermal response is demonstrated. Bilateral skin conductance responses were examined to same-different stimuli consisting of moderate intensity tones differing in pitch (S1, S2), to a response cue to make a unimanual button-press if the stimulation were judged the same (S3), and to feedback (S4). In the first two experiments in which a right-hand action was required, responses were larger to S2 than S1 on 'response', compared with 'no-response' trials. This was replicated in the second experiment where the same effect was also found to S3. In the third experiment the hand performing the action was varied; the influence of stimulus consequences on responses to S2 was replicated when the right hand performed the action; when the left hand was involved elevated responses to S2 occurred, irrespective of the perceptual judgement. In all experiments responses tended to be larger on trials where a correct judgement was made. The use of bilateral recording with a unilateral behavioural response confirmed the influence of effector functions on electrodermal responses. Hemispheric influences were contralateral and excitatory. The results were discussed in terms of multiple central determinants on electrodermal responses, the influence of cerebral laterality, and of sympathetic-somatic coupling.

Adult↗
PubMed1988

Acquisition of attention skill in pervasively hyperactive children.

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.

Attention↗
PubMed1987

A divided attention experiment with pervasively hyperactive children.

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.

Adolescent↗
PubMed1977

EEG spectra in XYY and XXY men.

Ten XYY, 13 XXY, and 45 control XY men were located in a birth cohort of tall men (non-institutionalized), and their EEGs were subjected to computer analyses. The XYY men showed a significantly slower alpha activity and more power in the 3.3--9.6 c/sec band than their XY controls. There were no consistent EEG differences between the XXY men and their controls.

Adult↗
PubMed1977

Electroencephalograms of XYY and XXY men.

Abnormal EEGs have been reported in XYY and XXY men located in psychiatric hospitals and prisons. In general, persons resident in institutions are more likely to exhibit EEG abnormalities than "normal" population, and this bias of ascertainment has complicated the interpretation of these results. The present study was conducted in Denmark. Chromosome determinations were made on 4,140 men selected from a birth cohort of 31,438 men. Twelve XYY and 16 XXY men were detected. Appropriate XY control groups were selected from the same population. The XYY men were found to have a significantly lower average frequency of the occipital alpha activity than their controls. The XYY and XXy men showed significantly more theta activity than the controls.

Adult↗