漢字の形態判断および意味的整合性判断における大脳半球機能差について

八田 武志

doi:10.4992/jjpsy.50.273

HEMISPHERE ASYMMETRIES FOR PHYSICAL AND SEMANTIC CONGRUENCY MATCHING OF VISUALLY PRESENTED KANJI STIMULI

TAKESHI HATTA

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JOURNAL FREE ACCESS

1979 Volume 50 Issue 5 Pages 273-278

DOI https://doi.org/10.4992/jjpsy.50.273

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Published: January 20, 1980 Received: July 02, 1979 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 : Several studies have investigated the laterality differences in the execution of so-called higher level cognitive tasks. However, it might be considered that the tasks which have been examined, such as a letter classification, dot numeration, and comparison between photograph of faces and caricature are not necessarily higher-order cognitive tasks.
The primary purpose of the present study was to examine the laterality differences in the execution of thought task: Semantic congruency decision making with respect to a frame of reference.
Twenty-eight right-handed university students participated in this experiment and made identification matching decisions (Condition 1) and semantic congruency decisions (Condition 2).
In the first condition, subjects decided whether the standard Kanji stimulus was identical to the Kanji in the comparison stimulus. Single Kanji as a standard stimulus was presented in the center of the visual field for 2sec and both a comparison stimulus consisting of a single Kanji and rectangle was exposed either in the left or the right visual field tachistoscopically.
The task for the subjects in the second condition was to decide the semantic congruency of Kanji. The fixation cross was presented centrally for 2sec and then a single Kanji paired with a rectangle was presented in the left or the right visual field. The stimuli were identical to that of the comparison stimuli in the first condition and consisted of single Kanji selected from four Kanji letters, “left”, “right”, “above”, and “below” paired with a rectangle. Single Kanji were located at one of the above four positions with respect to the paired rectangle. The Kanji was located at the semantically congruent position in a half stimulus and in another half, the Kanji was located at the incongruent position. That is, if the Kanji “left” was located at the right side of the rectangle, subjects were asked to make a “No” response and if located at the left side of the rectangle, subjects made “Yes” responses. In both conditions, subject's response latency was measured.
The results of the simple Kanji identification matching task (Condition 1) showed a non-significant but strong tendency toward left visual field superiority and suggested a right hemisphere specialization. This tendency of results was consistent with the results of the previous studies concerning Kanji recognition.
In the semantic congruency decision task (Condition 2), the results showed a strong right visual field superiority, although identical stimuli were employed in both conditions. The results obtained here suggest that in the execution of a higher-order thought task such as a congruency decision in addition to the ordinary semantic processing of Kanji stimuli, the left hemispere is superior to the right hemisphere. So the necessity of studies to investigate the hemisphere specialization of so-called higher-order cognitive processes more precisely was proposed.
Right : Hemisphere specialization for different levels of processing of visually presented Kanji letter with normal right-handed adults was investigated. A tendency toward left visual field superiority was found in the physical matching task and a significant right visual field superiority was found in the semantic congruency decision task. These results suggest that while in a lower level of processing single Kanji letters may be processed dominantly in the right hemisphere, in a higher level of thought processing of Kanji such as a semantic decision of the congruency with respect to the frame of reference, left hemisphere plays a superior functional role in processing.

Abstract

Hemisphere specialization for different levels of processing of visually presented Kanji letter with normal right-handed adults was investigated. A tendency toward left visual field superiority was found in the physical matching task and a significant right visual field superiority was found in the semantic congruency decision task. These results suggest that while in a lower level of processing single Kanji letters may be processed dominantly in the right hemisphere, in a higher level of thought processing of Kanji such as a semantic decision of the congruency with respect to the frame of reference, left hemisphere plays a superior functional role in processing.

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