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The present study examined the role of visual presentation mode (unilateral vs. bilateral visual fields) on attentional modulation. We examined whether or not the presentation mode affects the compatibility effect, using a paradigm involving two task-relevant letter arrays. Sixteen participants identified a target letter among task-relevant letters while ignoring either a compatible or incompatible distracter letter that was presented to both hemispheres. Two letters arrays were presented to visual fields, either unilaterally or bilaterally. Results indicated that the compatibility effect was greater in bilateral than in unilateral visual field conditions. Findings support the assumption that the two hemispheres have separate attentional resources.

To investigate hemisphere function of experts, Go experts and novices were given two Salthouse-type visuospatial tasks. In Experiment 1, stimuli of 4 digits in 6 cells were projected to the left (LVF) or right visual field (RVF). There was no prominent group difference in identification of digits and locations. In Experiment 2, stimuli of 4 digits in 16 cells were projected to the LVF or RVF. Go experts showed more accurate performance than novices. Both groups showed the same laterality, an RVF advantage, in the number identification. However, in the location identification, Go experts showed no visual field difference, whereas novices showed an RVF advantage. Based on these findings, the relationship between task demand and hemisphere function of experts is discussed.

The effects of handedness and script types on the difference in performance in a mental addition task by visual field were examined. Right-handers, nonfamilial left-handers, and familial left-handers who were all native speakers of Japanese were asked to add two numbers presented in the visual half-fields tachistoscopically. The two numbers were displayed either to one visual field (left or right visual field) or to the center. The numbers were displayed in Arabic, in Kanji, or in Arabic and Kanji numerals (one in Arabic and the other in Kanji: Mixed stimuli). The subjects were asked to add the two numbers and to state the sum orally. In the right-handers group, a right visual-field advantage was found for the Arabic condition but not for the Kanji or Mixed stimuli. On the other hand, in the nonfamilial and familial left-handers group, no visual-field difference in any of the conditions was found. These findings suggest that pattern of cerebral lateralization for familial and nonfamilial left-handers is the same but it is different from that of right-handers.

The relationships between hemispheric function and components of the imagery process were examined in patients with unilateral right and left brain damage and in intact adult subjects. In the image generation condition, subjects were required to mentally generate Katakana letters corresponding to Hiragana letters displayed on a CRT. The results for the intact adults suggested a left hemisphere superiority, but the unilaterally brain-damaged subjects showed no hemispheric difference in this task. In the imagery operation task (transformation or lateral translation), subjects were asked to find a genuine Kanji among distractors (pseudo-Kanji) that were constructed from two Kanji radicals (themselves real Kanji) that were either displayed in reverse order or shifted apart. The results for both intact adults and patients with unilateral brain damage suggest the superiority of the right hemisphere.

Thirty normal subjects were requested to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field or simultaneously one to the left and one to the right visual field. Arabic or Kanji numerals were used. Bilateral presentation was superior to unilateral presentation with both kinds of stimuli. In unilateral presentation, Arabic numbers were processed more proficiently in the left visual field and Kanji numbers in the right visual field.

Using three experimental tasks (lexical decision, naming and semantic classification), the relative contribution of various Kanji attributes in left and right visual field recognition was examined. The results showed that first, factors contributing to the left visual field processing of Kanji differed depending on the level of processing; second, in an early stage of processing, perceptual attributes such as the number of strokes was a strong contributing factor; and third, in a later stage both perceptual- and imagery-related attributes contributed strongly to left visual field or right hemisphere processing.

The visual field advantage for digits and random shapes recognition was investigated using both longitudinal and cross-sectional methods with children from ages from 4 to 6. A right visual field advantage for digit recognition and left visual field advantage for random shape recognition were found in the age 4 group. There was no evidence of developmental increase in visual field advantage with age, though there was slight gender difference in the development of visual field advantage. Comparisons of the results of longitudinal and cross-sectional methods revealed negligible differences.

In Exp. I, right-handed Ss made the "same" or "diffeeent" judgement to paired digits serially presented to the right and left visual field, and exhibited erroneous judgements in the left visual field lead condition. These results suggest the left hemisphere superiority. In Exp. II, the Ss were requested to make the "same" or "different" judgment and to press a key as fast as possible to the paired line orientation. The right visual field lead condition product more errors than the left visual field lead condition. This suggests the right hemisphere superiority. But no difference appeared between both conditions in the reaction time. The opposite hemispheric superiority, found in perceiving verbal and non-verbal materials in the 2 experiments, would be attributed to the basic difference in "perceptual" process.

Two hypotheses concerning functional hemispheric organization in schizophrenic patients were examined in two experiments. In the first experiment 35 chronic schizophrenics and 35 normal controls performed tactile-visual matchings with each hand. The results showed that the performance level of the schizophrenics was inferior to that of the normal controls, but did not show any hand difference. In the second experiment chronic schizophrenics and normal controls made intermanual matchings and intramanual matchings with successively presented nonmeaningful shapes. The results revealed that the intermanual matchings of the schizophrenics were significantly inferior to those of the controls but there was no subject group difference in the intramanual matchings. These results did not lend support to the hypothesis that schizophrenics have selective left hemisphere impairment, but suggest that there may be an interhemisphere interaction deficit in schizophrenic patients.

Two experiments were conducted to explore the hemispheric specialization for the visual recognition of Kanji. In Exp. I, effects of different processing strategies were examined. Reaction times obtained neither from physical identity matching nor phonological identity matching condition revealed any significant visual field differences. In Exp. II, hemispheric specialization for different levels of Kanji processing was investigated by those subjects who made both physical identity matching and semantic categorization matching. Results showed that RTs to the right visual field were shorter than that of the left in the semantic categorization matching, while no such significant visual field difference was revealed in the physical identity matching. Identical Kanji stimuli were used in both experiments to compare the relative strengths of the levels of processing and the effects of strategy on Kanji recognition. It is suggested from the present study that the effects of strategy in information processing is not strong enough to overcome the visual field difference while the visual field difference is strongly influenced by the levels of Kanji processing.

14 normal subjects were given two tactile-recognition tasks. Subjects were asked to match the tactually presented nonsense figures to the visual-recognition display on a Non-rotation task. On the Mental-rotation task subjects matched the tactile figures which were presented in various directions by means of mental rotation to the visual display. A greater superiority of the left hand on the Mental-rotation task was noted while on the Non-rotation task no differences between hands were shown. The right hemisphere may contibute more strongly to higher thought processes especially those which do not need verbal mediation.

The functional cerebral organization of minimal brain-damaged (MBD) children was studied by testing tactile-visual matching of concrete objects. The results revealed that left hand performance was significantly better than the right in the MBD children while normal controls showed no hand difference, and overall performance level was poor for MBD children. These findings are consistent with the view that tactile matching of concrete objects requires hemispheric synergy and that MBD children lack this synergy.

Naming times to single character Kanji, which consisted of small alphabetic letters, Kanji (Stroop stimuli), and solid lines, presented in the left or the right visual field were measured. When subjects tried to respond to Alphabet Stroop stimuli, they showed a greater interference effect in the case of right visual field presentation. Kanji Stroop stimuli yielded no visual field difference in the size of interference effect. These findings suggest that Kanji has a different property from phonetic symbols and a specialization of the right hemisphere for single character Kanji processing.

Hemispheric differences associated with Physical Identity Matching and Semantic Classification of Japanese characters (Kanji) were examined using visual event-related potentials and behavioural measures. Event-related potentials to the Kanji during matching tasks revealed hemispheric differences in the later components. Right hemisphere responses were larger than those or the left. The interaction of Types of Matches by Hemispheres was not significant. This interaction however was significant with the behavioural measure. On Semantic Classification Matching reaction times for right-visual-field Kanji were faster than those of the left field while no visual field difference was found for Physical Identity Matching. The sensitivity of both measures as indicators of laterality is discussed from the point of view of levels of processing.

Hemisphere specialization for two types of semantic comparative judgments were examined. In the first experiment a pair of Arabic numerals of different physical size were displayed and subjects were asked to judge if the physical size of the stimulus and the numerical magnitude were congruent or not by pressing the appropriate button. Reaction times were faster in the right visual field than in the left visual field. In the second experiment a pair of different physical sized Kanji representing concrete objects were displayed and subjects were required to judge if the physical size of the Kanji was congruent or not with the relative real life object size by pressing the appropriate button. Reaction times were faster in the left visual field. In the third experiment a pair of different physical sized Kanji representing numerical magnitude were displayed and subjects judged if the physical size of the Kanji and the numerical magnitude were congruent or not. Results showed a right visual field advantage and eliminated the possibility that Kanji complexity was the cause of the left visual field advantage in the second experiment. These results were interpreted as providing support for the proposal that there are two types of semantic comparative judgments, one relying on the verbal code and the other relying on the use of imagery, and suggesting that the former calls for stronger engagement of the left hemisphere while the latter calls for a stronger contribution from the right hemisphere.

The effects of aging on hemispheric specialization in verbal and visuo-spatial functions were examined by dichotic listening and tactile recognition tests. In the first experiment, thirty aged (65-91 year) intact subjects and university students were tested by a dichotic listening tape with pairs of two-syllable meaningful words. The results revealed an overall decline of scores in the aged subjects but there was no interaction between subject and the degree of right ear advantage. In the second experiment, subjects were asked to judged whether successively presented nonsense tactile stimuli to each hand were identical or not. Reaction times and accuracy rates of each hand of the aged subjects were inferior to those of the control subjects. However, no interaction was found between hand and subject group. Both experiments show that there is no evidence to suggest any selective deterioration or specialization of hemispheric function in the aged people, though overall performance level declines with age, which may be caused by short-term memory deficit.

The laterality difference in the execution of the higher-order cognitive task, categorization utilizing a superordinate concept, was examined. The subjects decided whether the two stimuli serially presented in the right or left visual field came under an identical category. In Exp. I, outline drawing stimuli were used and the RVF condition superiority in latency in the "same" response and LVF condition superiority in the "different" responses were demonstrated. These results were similar to those in the previous physical matching task and suggested that a superordinate concept was not in use to execute the present task. In Exp. II, vertically written verbal stimuli were used and the RVF condition superiority in both the "same" and the "different" responses were demonstrated. These results would suggest the superiority of the left hemisphere in the higher-order cognitive tasks.

A microcomputer controlled test of hemispheric time sharing was conducted on normal male and female students. Subjects engaged in a unimanual task involving sequential finger movement alone and in two conditions with concurrent cognitive activity. The verbal task interfered more with right than left hand activity in both male and female subjects. The spatial task interfered more with left than right hand activity in male subjects while female subjects did not show any hand differences. Possible sex differences in brain function were discussed.

Visual field differences and sex differences in a complex semantic processing task were examined. Two different print size Kana words which represented concrete objects were paired and displayed tachistoscopically to the left or the right visual field. Subjects decided if the relationship of the print size and real life size of the word pairs was appropriate or not by pressing a key. Results revealed that female subjects showed faster reaction times to the right visual field stimulation while males showed a tendency toward a left visual field superiority. Possible hemisphere difference in mechanisms between the sexes were discussed.

Hemispheric specialization for mental calculation and verbal tasks in abacus (Soroban in Japanese) experts and control subjects was tested using time-sharing tasks. In Experiment 1, the effects of auditorily presented mental calculation and news-listening tasks on sequential finger tappings were examined. The results revealed that in the mental calculation condition, abacus experts showed greater interference effects on left hand tapping, whereas control subjects showed greater interference effects on right hand tapping (as compared to left hand). In the news-listening condition, abacus experts showed no hand difference while the controls showed greater interference effects on the right hand. In Experiment 2, the effects of visually presented mental calculation and word-reading tasks on sequential finger tapping were examined. The results revealed that in the mental calculation condition, abacus experts showed a non-significant tendency towards greater interference in the left hand whereas the controls showed no hand difference. In the word-reading condition, both abacus experts and controls showed greater interference in the right hand than in the left hand. In Experiment 3, intermediate and upper-rank abacus experts performed a similar task to Experiment 1 under two instruction conditions. The results of this control experiment confirmed that a greater left hand reduction in calculation of abacus experts is not due to subject's cognitive mode but due to the amount of abacus learning experience. These data suggest that (1) learning experiences can affect the pattern of cerebral specialization through the change of approaches to perform cognitive tasks, and (2) the right hemisphere engages in mental calculation for the abacus experts whereas the left hemisphere contributes to mental calculation in ordinary people having no experience of abacus learning.

Study of matching judgment was designed to demonstrate an effect of lateral onset asynchrony in left-handed subjects, 7 males and 8 females. Japanese Hirakana letters or random forms were presented to one visual field first and to the other visual field second. 15 left-handers were requested to judge whether the successively presented stimuli were "same" or "different." The results showed that for both types of stimuli there are no differences in accuracy of matching judgement whether the standard stimulus was presented to the right visual field first or to the left. These results indicate that the left-handed subjects may have a tendency toward hemispheric equi-potentiality for recognition of both verbal and non-verbal materials.

Possible hemispheric functional differences between adolescent partial English-Japanese bilinguals and Japanese monolinguals were examined with a reversed auditory Stroop test. Subjects were requested to press their left/right hand button when they heard the target Japanese word "Otoko (male)/Onna (female)" as fast as possible. In one condition, the word and the speaker's sex weed congruent and in the other condition they were incongruent. The results of the reaction times showed that Stroop effects appeared with both responding hands in the bilingual group. On the other hand, the results of the monolinguals revealed that the Stroop effect was shown only with the left hand and not with the right hand. These results suggest that in nonproficient bilinguals, the right hemisphere may be involved in processing word meaning.

The validity of lateral eye movement (LEM) as an index of hemispheric activation was examined with a series of experiments. LEMs were measured to verbal and spatial questions (Experiment 1), word detection and emotion detection tasks (Experiment 2), and to negative and positive emotions (Experiment 3). The results of these three experiments showed that LEM is not a sensitive index of hemispheric activation. Experiment 4 showed that individual differences in LEM patterns is relatively stable and may reflect some personality traits.

The validity of Bowers and Heilman's hemispace hypothesis (Neuropsychologia 18, 491-498, 1980) that "laterality effects depend upon the spatial condition in which a stimulus is presented" was examined in two tactile bisection experiments (one with adults and the other with kindergarten children). Three indices: absolute error, constant error and directional error were employed to measure the accuracy of the two hands and hemispaces. The results did not support the hemispace hypothesis, though weak spatial condition effects appeared for female subjects.

8 boys and 8 girls at each three age levels (2nd-, 4th-, and 6th grade) performed a tactile-visual recognition task, in which a tactually palpated object shape had to be matched with its analogue on a visual display. The performances of the left and right hand were compared. The results indicated that the performance of the left hand was more accurate than that of the right hand for 6th grade children while no significant difference between hands emerged in 2nd- and 4th grade children. A sex difference was found, with the right hand superior to the left hand in females but not significantly different in males. These results are discussed in relation to the development of hemisphere specialization.

A new cognitive test for hemispherecity, based on the knowledge of hemispheric functional differences, was developed. In the first experiment, fifty subjects were examined their preferences for either visual-spatial or visual-verbal processing to the stimuli to which both types of processing were available. In the second experiment, ERP (Event Related Potentials) were measured in the two conditions: One, subjects processed the stimuli used in the first experiment as the visual-nonverbal stimuli, the other, subject processed the same stimuli as the visual-verbal stimuli. ERP from the left and the right hemispheres differed between both conditions in the later components. In the third experiment, both groups of subjects who preferred visual-verbal processing and visual-nonverbal processing were asked to report the Hiragana words presented tachistoscopically to the left or the right visual field. The former group of subjects showed a significant right visual field advantage while the latter group of subjects showed no visual field difference. These results confirm that the newly developed test for hemispherecity has appropriate validity and reliability.

Observed differences in hemispheric dominance of visual function, attributed to culturally based experience of Japanese and American subjects, need systematic exploration.

To examine whether concurrently presenting surrounding scripts affect single Alphabet recognition, subjects compared letters which appeared in the left or the right visual field to a previously presented sample letter. Four different comparison stimuli were prepared, target letter embedded in same-type print letters, in different-type letters, in different kinds of characters, and in blank space (control). The results indicated that both RTs for letter matches and visual field differences were different depending upon the kind of letters that surrounded the target Alphabet. This finding strongly suggests that letter recognition is affected by the presence of neighbouring letters, and further that the nature of the surroundings can differentially affect cerebral hemispheric functioning.