情報処理様式にみられる大脳両半球機能の非対称性

大岸 通孝

doi:10.4992/jjpsy.49.257

HEMISPHERIC DIFFERENCES IN THE MODE OF INFORMATION PROCESSING

MICHITAKA OHGISHI

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JOURNAL FREE ACCESS

1978 Volume 49 Issue 5 Pages 257-264

DOI https://doi.org/10.4992/jjpsy.49.257

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Published: January 20, 1979 Received: February 27, 1978 Available on J-STAGE: July 16, 2010 Accepted: - Advance online publication: - Revised: -
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Date of correction: July 16, 2010 Reason for correction: - Correction: ABSTRACT Details: Wrong : Many laterality studies have demonstrated that the left hemisphere (LH) is considered to be specialized for verbal functions while the right hemisphere (RH) is seen as carrying out nonverbal activities. However, several recent studies which pose new dichotomies about hemispheric asymmetries in place of the dichotomy between verbal and nonverbal functions, have emphasized the dimension of time as the cerebral function. These studies have suggested that the LH processes information sequentially or in a serial fashion, while the RH does so simultaneously or in a parallel fashion, though it is important to note that some studies have indicated that a serial vs. parallel processing difference between two hemispheres is a concomitant of hemispheric predilection of nominal vs. physical analysis.
The experiments reported here were aimed at examining whether or not a difference in information processing exists between the two hemispheres.
Stimuli tachistoscopically presented to either the right or left visual field, consisted of a combination of two, three, or four physically simple Japanese katakana letters. In Normal Condition, letters were presented in upright position, while in Inverted Condition, letters were presented upside down. Righthanded subjects were required to respond “same” by pressing a key as fast as possible whenever all letters were identical, and to respond “different” by pressing another key whenever one letter differed from the rest.
It was predicted that there would be a linear increase of reaction times with number of letters in the set when information was transmitted to the LH, whereas reaction times wouldn't increase as a function of set size when information was transmitted to the RH. It was also hypothesized that when letters were categorically perceived by being analyzed nominally or verbally, subjects would be apt to make as many “same” responses as “different” responses; when letters were analyzed physically or nonverbally, there would be more “different” responses than “same” responses.
The results of Normal Condition were as follows:
1. The LH made as many errors to the “same” stimuli as to the “different” stimuli whereas the RH made more errors to the “same” stimuli.
2. There were hemispheric differences in the slope of reaction times against number of letters in both the “same” and “different” responses; the reaction times of the LH increased linearly while those of the RH hardly changed.
The results of Inverted Condition were as follows:
3. Both hemispheres made more errors to the “same” stimuli than to the “different” stimuli.
4. The “different” reaction times of the LH increased linearly as a function of set size although the reaction time pattern of the “same” responses didn't indicate a clear-cut trend because of many errors being made in the “same” responses of the LH. The reaction times of the RH didn't change.
5. The reaction times of the LH were significantly shorter in Inverted Condition than in Normal Condition.
These results suggest not only that the RH is characterized as a parallel processor, but also that the LH is characterized as a serial prosessor even when matching was made in the stage of physical analysis which precedes the stage of verbal analysis.
Right : To examine hemispheric differences in the mode of information processing, 24 normal right-handed subjects were required to make same or different responses to a set of letters varying in number from two to four which were all identical or contained one letter differing from the rest. When letters were presented in the normal upright position, the left hemisphere showed serial processing wherein reaction times increased as a function of number of letters. The right hemisphere, however, showed no increase of reaction times, i.e. parallel processing. When letters were presented in the inverted upside-down position, the left hemisphere showed partial serial processing, despite letters being analyzed physically. The results suggest that visuospatial analysis doesn't always force parallel processing in the left hemisphere.

Abstract

To examine hemispheric differences in the mode of information processing, 24 normal right-handed subjects were required to make same or different responses to a set of letters varying in number from two to four which were all identical or contained one letter differing from the rest. When letters were presented in the normal upright position, the left hemisphere showed serial processing wherein reaction times increased as a function of number of letters. The right hemisphere, however, showed no increase of reaction times, i.e. parallel processing. When letters were presented in the inverted upside-down position, the left hemisphere showed partial serial processing, despite letters being analyzed physically. The results suggest that visuospatial analysis doesn't always force parallel processing in the left hemisphere.

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