Alan Glass

Individual Differences in Thinking: cognitive and neurophysiological perspectives

This paper explores the neglected area of categories of individual difference in human cerebral function. During thinking and decision making, it is hypothesised that different people process the same information in different ways, using different areas of the brain. Recent work suggests that individuals can be categorised into a small number of consistent groups of thinking, or cognitive, style. The different ways of processing reflect two basic dimensions of cognitive style. A simple computer‐presented method of determining cognitive style has been developed. It is probable that these styles have an underlying cerebral basis. The styles are likely to be related to cerebral orientation. The specialisation of one cerebral hemisphere for verbal function and the other for visuo‐spatial has been long established. Hemispheric specialisation has been associated with the right hemisphere being the location of the visuo‐spatial and the left the verbal function, although evidence for this has been sometimes confl...

Cognitive style and individual differences in EEG alpha during information processing

Abstract When presented with a task, it was hypothesised that different people tend to process the same information in different ways, using different areas of the brain, depending upon their cognitive style. The study used 15 adult subjects, who received the computer‐presented Cognitive Styles Analysis to assess their positions on two basic cognitive style dimensions: the Wholist‐Analytic and Verbal‐Imagery. In a computer‐presented task, subjects were asked to view words presented singly at a rate of two, five and 10 words/second and in pairs at five and 10 word‐pairs/second and to press a key when a word appeared which was in a target conceptual category (e.g. a fruit). The task comprised eight 30‐second trials. During the task, alpha band EEG was monitored at 15 locations. For the Wholist‐Analytic style, Analytics had, over all tasks, lower alpha power relative to the Wholists at all locations, and particularly posteriorly. With the Verbal‐Imagery dimension, there was style‐hemisphere effect, with Verb...

EEG differences and cognitive style.

Individuals differences in information processing related to cognitive style were investigated by EEG recording during cognitive tasks. Fifteen adults received the Cognitive Styles Analysis which assessed their positions on two dimensions: the wholist-analytic and the verbal-imagery. The EEG from midline, paramedial and lateral electrode clusters was recorded, while subjects viewed words presented at different rates. A button was pressed when a word was in a target conceptual category. Off-line analysis produced spectral powers for delta, theta, alpha, beta 1, beta 2 and gamma bands. For the midline, the wholists had higher output than analytics in theta and alpha, but lower in gamma. In the paramedial cluster, verbalisers had greater right power than imagers for all bands except alpha. Further, the overall power was greater on the right for imagers than verbalisers frontally, and the converse occipitally. In the lateral grouping, the wholist-verbalisers had greater overall power left antero-temporally than other sub-groups.

Hemispheric asymmetry of EEG alpha activation: Effects of gender and familial handedness

Twenty-four male and twenty-four female undergraduates took part in an experiment to investigate the effects of gender and familial handedness on hemispheric activation during numeric and visuospatial thinking. Each gender group was divided into twelve subjects with close left handed relatives and twelve subjects without. All subjects were overtly right handed. EEG alpha activity was recorded from left and right occipital and parietal regions with respect to mastoid references while the subjects performed numeric tasks with eyes open and with eyes closed, a face-recognition and a tactile-discrimination (figural-unification) task. EEG alpha power was quantified during these conditions and during relaxed wakefulness with eyes open and eyes closed. Relative activation, (suppression of alpha activity from rest) of left and right parietal regions during numeric and spatial tasks was found to depend upon gender and familial handedness. Males, not females, tended to switch from left hemisphere activation during face recognition. Irrespective of gender and to some extent of task, a tendency towards greater activation of the right hemisphere was associated with the possession of left handers among close relatives.

Cognitive and EEG asymmetry

Several recent reports concerning the relationship of EEG asymmetry to cognition were evaluated. Technical and interpretive shortcomings of some papers minimizes their significance with respect to this issue, whereas several findings support the notion that EEG asymmetry occurs in association with cognition per se.

Asymmetries in the CNV over left and right hemispheres while subjects await numeric information

Abstract The contingent negative variation (CNV) was recorded from frontal and central electrodes in one left-handed and 12 right-handed subjects. The CNV was elicited by tachistoscopically exposed visual stimuli comprising a warning spot followed by a numeral. Numerals so exposed had to be memorized (cumulative condition), added (arithmetic condition), or checked to ensure that all were zeros (repetitive condition). The arithmetic and cumulative tasks were designed to potentiate any expectancy mechanisms in the hemisphere dominant for verbal processes. The repetitive task was intended as a neutral control. All three tasks elicited CNVs whose amplitude was greater over the hemisphere contralateral to the preferred hand. The results are discussed in terms of possible relationships with handedness and the lateralization of cerebral function.

Comparison of the effect of hard and easy mental arithmetic upon blocking of the occipital alpha rhythm.

The intensity of blocking of the alpha rhythm of the EEG induced by the solution of five Hard mental multiplications has been compared with the intensity of blocking induced by five Easy mental multiplications in 36 normal subjects. From predictions derived from the application of two hypotheses concerning the intensity of blocking, it would be anticipated, firstly, that blocking would be more intense in the Hard tasks, if their solution required increased mental concentration and, secondly, that insofar as “higher thought” processes are more extensively required in the solution of Hard tasks, then blocking would be less intense in Hard tasks than in Easy tasks. However, the findings of the experiment have been that blocking is of the same intensity in tasks of both kinds. Possible reasons for this are discussed. Hard tasks differed from Easy tasks, with regard to the relation of EEG changes and performance. It is thought that different mechanisms may underly the solution of the two types of task.

Asymmetries of the contingent negative variation (CNV) and its after positive wave (APW) related to differential hemispheric involvement in verbal and non-verbal task

The CNV and the subsequent positive wave (including both the P300 wave and the slow positivity following it) were recorded at left and right frontal and central electrodes during the performance of tasks in which nine right-handed subjects (male and female) had to determine whether S1 and S2 were the same or different. In one task, works had to be matched for meaning while in a second, faces had to be matched for identity. Words elicited CNVs which were more negative over left than right frontal regions. This effect was reversed when the stimuli were faces. Since the CNV is presumed to reflect processes of anticipation rather than stimulus processing, the asymmetry cannot be explained in terms of the lateralisation of neural mechanisms specialised for the analysis of verbal or visuospatial stimuli. Instead the observation is regarded as evidence for mechanisms of lateral activation of a more general nature than would be necessary for the facultative selection of cognitive mode. The amplitude of the CNV relative to baseline was affected by the amplitude of P300 response to S1. This was larger to faces than words in both hemispheres. A small asymmetry in the positive wave following S2 was observed, the amplitude being greater over the right hemisphere for words and over the left for faces. This is interpreted in terms of the subjective probability of the two types of stimulus for a hemisphere ill-equipped to receive them.

Individual Differences in the Asymmetry of Alpha Activation

Asymmetry in the distribution of the alpha rhythm first received attention during the early seventies (Morgan, McDonald and MacDonald, 1971; Galin and Ornstein, 1972a & b; Glass and Butler, 1973; Butler and Glass, 1974). The effect was attributed to the activation of lateralised mechanisms serving language and ‘visuospatial’ functions and was therefore perceived as a non-invasive method of investigating hemispheric specialisation. It has recently become clear that alpha asymmetry varies systematically as a function of gender and handedness. In this chapter we shall consider the significance of this variation in terms of individual differences in the structural and dynamic aspects of hemispheric specialisation.

Speed of work and EEG asymmetry

EEG from O1 and O2 was recorded from twelve subjects (6 male and 6 female) whilst they carried out a paced inspection task at five separate task speeds. Peak alpha activity was analysed using a spectral analysis technique. The results suggested that when subjects were working at a speed 25% faster than their self-chosen pace they were using predominantly their right hemisphere, whereas then they were working at 25% slower they were using mainly their left hemisphere. It was suggested, based on earlier literature, that subjects may be processing information about the task in different ways at different task paces: A sequential processing strategy is being used at the slow pace whilst a parallel or Gestalt processing strategy is being used at the fast pace.