PubMed Health⌕ Search

Biomedical subjects

C Hardyck

Publications and source records attributed to C Hardyck.

12 recordsLinked to original sources
PubMed1986

Cerebral asymmetries and experimental parameters: real differences and imaginary variations?

The basic conditions and stimulus parameters of the paradigm usually used to study visual field-hemisphere differences are reviewed. An argument is presented that a majority of published reports using this paradigm are, in fact, the same basic experiment. The similarity of many parameters over experiments constitutes a set of effects whose influence on our interpretations are not determinable since these parameters are seldom varied. Examples of unsuspected effects on lateralization are drawn from three studies carried out by the author and his colleagues.

Attention↗
PubMed1985

The eyes have it: exposure times and saccadic movements in visual half-field experiments.

Several tachistoscopic visual half-field experiments using exposure times in excess of 150 msec have been reported and arguments have been put forth justifying this procedure. An experiment was done investigating visual field accuracy under conditions where eye movement was allowed, following parafoveal exposure. Two control experiments were done to evaluate the viewing conditions. When eye movement is permitted, accuracy in both visual fields reaches 100%. It is concluded that visual field differences found with exposure times greater than 150 msec are due to the active cooperation of the subjects and not due to the justifications advanced by experimenters using long exposure times.

Adolescent↗
PubMed1985

Orienting attention within visual fields: how efficient is interhemispheric transfer?

Five experiments are reported examining the effect of attentional orienting on lexical decisions within visual half-fields. In Experiment 1, following baseline performance, subjects were instructed to improve performance to the right or left of the fixation point. In Experiment 2, trials were run in blocks with all items to one side of the fixation point. In Experiment 3, completely valid position indicators as to the location of the next item to be shown were presented prior to the stimulus item. In Experiment 4, to examine practice effects, no instructions or cuing were given to subjects. In Experiment 5, subjects were urged to improve performance, but with no instructions as to location. As a summary of our results, it can be stated that (a) consistent visual field differences in lexical decision performance are present, even when subjects were informed, prior to viewing, of the spatial location of the next stimulus item. (b) Lexical decision information initially input to one cerebral hemisphere is primarily processed in that hemisphere. Interhemispheric transfer of this type of language information seems to be done primarily as the end product of a cognitive process.

Attention↗
PubMed1984

Choosing sides: on the variability of language lateralization in normal subjects.

We report test-retest reliabilities and individual asymmetries for a lateralized lexical decision task. Although acceptable reliability was found for word recognition, most subjects did not show statistically significant asymmetries, despite a robust right visual field group advantage. Inter-subject variability was unrelated to sex, handedness, or familial sinistrality. We offer some suggestions as to why these differences are to be expected in the study of normal populations.

Adult↗
PubMed1980

Role of cerebral hemispheric processing in the visual half-field stimulus-response compatibility effect.

Two experiments were conducted to test theories of the stimulus-response (S-R) compatibility effect. Stimuli presented above and below a fixation point in the left and right visual field signaled choice responses in the midsagittal plane. Even though the duration of stimulus presentation in Experiment 1 was sufficiently brief, such that the possibility of eye movements was precluded, a visual half-field S-R compatibility effect was still obtained. That such an effect is found when it can be adequately specified to which hemisphere stimulus information is presented suggests that an explanation in terms of cerebral laterality factors be considered. The second experiment employed arbitrary symbols to represent the spatial property of stimuli used in prior experiments, and a similar pattern of results was obtained. These results are discussed in terms of a functional view of cerebral organization.

Dominance, Cerebral↗
PubMed1977

Left-handedness.

Explore the source record for details and available documents.

Cerebral Cortex↗
PubMed1976

Left-handedness and cognitive deficit.

Intellectual and performance measures were taken on 7688 school children tested on three behavioral measures of handedness and one measure of eyedness. Test results were compared against all combinations of handedness and eyedness and against a measure of socio-economic level. No relationships of any kind were found. Comparisons of the present results are made against 33 studies concerned with possible deficits associated with left-handedness. The results of the present study combined with a review of the majority of studies on deficit and handedness strongly suggest that the hypothesis of no difference in intellectual and cognitive performance between right- and left-handed subjects can be accepted as true.

Attention↗