Curtis Hardyck

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.

Subvocal speech and comprehension level as a function of the difficulty level of reading material

Muscle action recordings (electromyograms) were taken from the larynx, chin-lip, and forearm flexor of three groups of S s during the reading of materials judged to be conceptually easy and difficult. A normal group had electromyograms recorded during reading. A feedback group was required to keep laryngeal muscle activity at nonreading relaxation levels during reading through use of an audio signal activated by any increase in muscle action in the larynx. A control group was required to maintain similar relaxation of the forearm flexor by the same feedback apparatus. All S s took examinations on the material read. The laryngeal feedback group did significantly less well on comprehension of the difficult material than the other groups. The mediating effects of speech at a subvocal level in information processing are discussed and a theoretical model developed.

Cerebral lateralization of function and bilingual decision processes: Is thinking lateralized? ☆

Abstract Four experiments utilizing tachistoscopic presentation of verbal and spatial stimuli to visual half-fields are presented. Three experiments failed to find any cerebral lateralization effect of the type predicted from existing models of cerebral lateralization processes. One experiment found marked lateralization effects. Since the experiments differ only in the ratio of trials to experimental stimuli, it is argued that cerebral lateralization experiments are detecting only a memory process occurring after subjects have learned all the stimuli to be presented. When new stimuli are presented on each trial, no cerebral lateralization effects are found, suggesting that active ongoing cognitive processing is independent of lateralization.

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.

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.

Previous experience and the learning of computer programming: The computer helps those who help themselves.

Recent developments in mathematics education indicate that previous experience is the best predictor of high school math achievement scores. Given this information we hypothesized that previous experience with computers would serve as a predictor of performance in college computer science courses. Also of interest was the possible interaction of gender, prior computing experience and computer science course performance. To examine these issues, we designed and administered a questionnaire to students across two semesters of the first year Pascal programming course at the university level. Roughly one-quarter of the students enrolled across the two semesters were female. Results show that males have more prior experience, especially in advanced computer science topics, than females, and that much of this prior experience is gained outside of school through “hacking” and unguided exploration. Amount of prior computing experience was found to predict course performance for males. For females very little prior experience was reported and this limited amount of experience was not predictive of course performance. The question of why women have so little prior experience with computers and are so sparsely represented in computer science courses is addressed.

A Model of Individual Differences in Hemispheric Functioning

Publisher Summary This chapter focuses on the differential functioning of the human cerebral hemispheres and reviews various models of hemispheric functioning. The Semmes model is based on the results of studies of brain function in somesthesis on patients with penetrating brain injuries. The results of these studies indicated that responses were different for the right and the left hand over several lesion locations. The model is based primarily on the high degree of cerebral lateralization characteristic of right-handed individuals who have a negative family history of left-handedness. The Levy model characterizes the left-handed as a possible evolutionary retrogression, owing to some failure to develop full lateralization. The chapter presents and evaluates a proposed model of individual differences in hemispheric functioning as related to familial handedness. The proposed model has an advantage over existing models of cerebral function. The model is consistent with the vast majority of published research on hemisphere function and specialization, including experimental work on normally functioning subjects and clinical studies of lesion damage.

Spatial frequencies and the cerebral hemispheres: contrast sensitivity, visible persistence, and letter classification.

The hypothesis that the two cerebral hemispheres are specialized for processing different visual spatial frequencies was investigated in three experiments. No differences between the left and right visual fields were found for: (1) contrast-sensitivity functions measured binocularly with vertical gratings ranging from 0.5 to 12 cycles per degree (cpd); (2) visible persistence durations for 1- and 10-cpd gratings measured with a stimulus alternation method; and (3) accuracy (d’) and reaction times to correctly identify digitally filtered letters as targets (L or H) or nontargets (T or F). One significant difference, however, was found: In Experiment 3, a higher decision criterion (ß) was used when filtered letters were identified in the right visual field than when they were identified in the left. The letters were filtered with annular, 1-octave band-pass filters with center spatial frequencies of 1,2,4,8, and 16 cpd. Combining four center frequencies with three letter sizes (0.5°, 1°, and 2° high) made some stimuli equivalent in distal spatial frequency (cycles per object) and some equivalent in proximal spatial frequency (cycles per degree). The effective stimulus in the third experiment seemed to be proximal spatial frequency (cycles per degree) not distal (cycles per object). We conclude that each cerebral hemisphere processes visual spatial frequency information with equal accuracy but that different decision rules are use

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.

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.