An EEG correlate of the Archimedes spiral after-effect and its relationship with personality

Previous work has demonstrated a relationship between the Archimedes spiral after-effect (SAE) and dysthymia-hysteria. The aim of the present study was to discover whether there was any EEG correlate of this relationship. As subjects 20 dysthymics, 17 hysterico-psychopaths, and 9 normals were used, comparisons being made between the SAE and various EEG parameters. These included the alpha index and latency of alpha return on eye-closure, following fixation of a rotating spiral. Using various criteria of the latter measure a consistently significant positive correlation was found between the SAE and the extent to which the return of alpha was delayed by visual stimulation. Significant correlations were also found between alpha index and SAE, and alpha index and alpha latency. In addition, previous group differences in sedation threshold and SAE were confirmed, although there were low correlations between the EEG measures and sedation threshold.

It was concluded that subjects having more activated EEG records tend to report longer subjective SAE's and to show a greater delay in the return of alpha alter visual stimulation. In terms of personality type obsessionals and psychopaths seem to show the greatest differences in this respect. These results are thought to throw some light on the physiological basis of Eysenck's excitation-inhibition theory of personality.     

Sedation threshold and Archimedes spiral after-effect: A follow-up of their use with civilian psychiatric patients

In the study reported here an attempt was made to confirm, on a more heterogeneous group of civilian patients, some previous work on sedation threshold and spiral after-effect in young military patients. Sedation threshold and spiral after-effect data were collected in thirty-eight neurotic and nine psychotic patients. The main findings of the study were as follows: (1) The practicability and reliability of the sedation threshold technique used is not restricted to the experimental setting in which it was originally devised. The method can on the contrary be applied under a variety of clinical conditions. (2) No significant differences were found in the uniformly high sedation threshold and spiral aftereffect scores of patients suffering from neurotic depression, obsessional neurosis, and chronic anxiety. Further, civilian dysthymics as a whole did not differ significantly on either test from military dysthymics. The previous work on neurotics was thus confirmed. (3) Previous findings (with military psychotics) of a significant negative correlation between sedation threshold and spiral after-effect were confirmed in the present group of schizophrenic patients.

The advantages of a psychophysiological approach to personality were reaffirmed and the possible usefulness of the sedation threshold and spiral after-effect as tools for differential diagnosis was discussed.     

Phenobarbitone and kinaesthetic after-effect

The effect of phenobarbitone (phenobarbital), predominantly a central depressant, on kinaesthetic after-effect was examined. The subjects were selected after a preliminary testing with the Maudsley Personality Inventory. They were classified into two groups: extraverts and introverts. The drug was used at different dose levels. A 2 × 4 randomized block design was replicated ten times. The study supports the following conclusions: (a) the extraverted subjects show larger kinaesthetic after-effect than introverted subjects under placebo condition; (b) phenobarbitone has no effect on kinaesthetic after-effects in extraverted subjects except in small doses (30 mg) which reduce the size of the effect; (c) the drug in larger doses (60 mg and 100 rng) produces a significant increasing effect in the introverted group.     

The origin of the after-effect of movement

Previous experimental work on the origin of the after-effect of seen movement is discussed and the relevance of the argument from transfer, which is generally used to demonstrate that the effect is central, is brought into question. The problem is reformulated in terms of whether a retinal contribution is necessary throughout the aftereffect and experiments are described which support the hypothesis that it is necessary. It is suggested that perception of the movement after-effect also involves normal movement perception, which itself is dependent on the integrity of cerebral functioning.     

Executive functions and extraversion

Executive functions and extraversion have been linked to similar neurological substrates. Participants were tested on a variety of tasks that assessed performance on three components of executive functioning (i.e., shifting, updating, and inhibition) and two measures of extraversion (Eysenck Personality Questionnaire-Revised and Carver and White’s BIS/BAS scales). More extraverted participants showed different patterns of executive function performance than the more introverted participants. Extraverts performed best on more difficult tasks and on updating tasks. Conversely, introverts performed best on set shifting tasks. These results suggest that executive functioning strengths differ based on degree of extraversion.     

On the figural after-effect

Two experiments were carried out on the figural after-effect. The first was intended to discover whether the figural after-effect did in fact take place with statistically significant universality. The method of scoring is relevant to the question of statistical significance, but at the best the figural after-effect appears to occur in only a slightly significant manner under the first conditions used. These involved the viewing of a single circle displaced to the left of a fixation point (the inspection-figure) and so placed that if it were superimposed on the second figure—which consisted of two squares on either side of the fixation-point—the circle completely encircled the left-hand square. The second figure is called the test-figure. The fixation point of the inspection-figure was fixated for 25 seconds with one eye, and then the test-figure was substituted and viewed with the opposite eye. A decision was then given by the observer as to the relative size of the squares. Eye-dominance did not appear to be connected with these after-effect processes.

In the second experiment, however, the statistical significance of the occurrence of the after-effects was undoubted. There were two changes in experimental conditions: the instructions to the observers were changed somewhat and a second circle was introduced into the inspection-figure. No difference of any kind was found to occur in the figural after-effect when the test-figure and inspection-figure were displaced horizontally and when they were displaced veitically, and there appeared to be a precisely opposite effect to that predicted when the test-figure and the inspection-figure were actually superimposed.

The most important finding was that, whereas in the first experiment the after-effect occurred with a frequency which was barely significant statistically, it occurred on every occasion under the different conditions of the second experiment.     

The relationship between extraversion and time of data collection

According to Eysenck's theory introverts, because they are cautious or low in impulsivity, should fulfill their mandatory experimental credit hours by volunteering for experiments early in the semester while extraverts should wait until the last minute. Data collected during the 5th and 15th week of the semester and after the semester was completed provide modest support for the hypothesis. Extraversion scores for the last session were significantly higher than the prior four sessions in an a priori contrast (t = 3.48, df = 152, P < 0.001) but scores from the 15th week while higher than the 5th, were not significantly higher (t = 1.30, df = 152, P = 0.20).