Israel Nachshon

Developmental aspects of visual hemifield differences in perception of verbal material.

Abstract The effect of acquisition of reading on visual field asymmetries for verbal material was investigated in school-age children. Contrary to the expectation that acquisition of differential scanning tendencies will operate on perceptual asymmetries, it was found that right visual field superiority which was independent of scanning direction appeared at the fifth grade. This, and the presence of slight left field superiority at the age when reading is initially acquired, suggests that hemispheric dominance and its attributes, parallel and sequential pattern recognition processes, is the major factor which determines the field preference for verbal material.

Hand preference in sequential and spatial discrimination tasks.

Hand preference in sensorimotor discrimination tasks was tested on 80 right handed subjects in four experiments. One set of experiments compared the abilities of the two hands to perform sequential tasks. The other set compared spatial abilities of the two hands. Within each set one experiment involved unimanual performance, and the other bimanual performance. The results showed that subjects performed better with their right hand on the bimanual sequential task, and better with their left hand on the bimanual spatial task. No hand preference was found in the unimanual tasks. The results are interpreted as reflecting the differential sensorimotor dominance of the left and right hemispheres for sequential and spatial tasks respectively.

Lateral Preferences of Hand, Eye and Foot: Relation to Cerebral Dominance

Patterns of lateral preferences of hand, eye and foot were analyzed on 7364 children, differing in race (black and white) and sex. Right hand and foot preferences were found in over 80%, and right eye preferences were found in over 50% of the subjects. No sex or race differences appeared in left-right preferences. However, significantly more females than males, and more blacks than whites, showed variable foot preference. Further analyses of cross preferences indicated that about 40% of the subjects showed consistent lateral preferences of hand, eye, and foot (about 37% right, and about 3% left), whereas the other 60% were divided among ten groups of different preference combinations. The three lateral measures were correlated to differing degrees. The data were interpreted as showing the effects of cerebral dominance on lateral preferences of hand, eye and foot. The effects seemed to be considerably stronger for hand and foot than for eye preferences. Due to a lack of supporting data, interpretation of race differences in variable foot preference must be considered tentative.

Responses of paranoid and nonparanoid schizophrenics in a dichotic listening task.

Differences in attentional processes between normals, paranoid schizophrenics, and non paranoid schizophrenics were studied by delivering dichotically presented digits for identification. Thirty paranoid schizophrenics (20 acute and 10 chronic), 30 non paranoid schizophrenics (20 acute and 10 chronic), and 20 normal controls were tested. The data were analyzed in terms of the overall level of correct identification of stimuli presented to the two ears, the number of shifts in report from one ear to the other, and the magnitude of ear differences in recall. The results showed that overall level of performance was higher for the normals than for the schizophrenics; the number of ear shifts was greater for normals and non paranoid than for paranoid schizophrenics; and ear differences were biggest for the paranoid schizophrenics and smallest for the normals. The results were interpreted in terms of differences in attentional style and rate of information processing.

Hemispheric dysfunctioning in schizophrenia.

Reinterpretation of old data (J. Nerv. Ment. Dis., 164:247-252, 1977), which showed greater right ear superiority effects for schizophrenic patients than for normal controls in dichotic listening, lends support to the assumption of left hemisphere overactivation among schizophrenics. This overactivation seems to be more pronounced among paranoid than among nonparanoid schizophrenics.

Birth Order and Lateral Preferences

Associations between birth order and lateral preferences of hand, eye and foot were examined in a sample of 6436 black seven year old boys and girls whose mothers participated in the Collaborative Perinatal Project (CPP) in Philadelphia. Overall, most of the subjects (87%) showed right hand preference, and the majority of subjects showed right eye (55%) and foot (63%) preferences. Analysis of cross preferences indicated some tendency for a consistent right side orientation. However, patterns of lateral preferences were similar for both boys and girls across seven birth order groups. The data were interpreted as showing that birth order and lateral preferences are not interrelated.

CROSS‐CULTURAL DIFFERENCES IN DIRECTIONALITY*

Abstract The assumption that the directions of writing single letters and series of letters in a given language affect the directional preferences for reproducing single and multiple stimuli, respectively, was tested on three groups of subjects with different reading and writing habits; English readers, Hebrew readers, and Arabic readers. The subjects were presented with single stimuli and with series of stimuli for reproduction, and the horizontal directions of their responses were recorded. Confirming the hypothesis, the data pointed to the complexities of the effects of reading and writing habits on directional preferences among readers of different languages.

Violent Behavior and Cerebral Hemisphere Function

Experimental support for the hypothesis that violent behavior is associated with left-hemisphere dysfunction is scarce. This study examines the association between crime, violence, and left-hemisphere dysfunction using measures of hand, eye, and foot dominance within a sample of 1,066 males born and raised in Philadelphia between the ages of 10 and 18 years as part of the Biosocial Study conducted at the Center for Studies in Criminology and Criminal Law at the University of Pennsylvania. Overall there were no significant differences between offenders and non-offenders in measures of hand and foot preferences. However, for eye preference, there were significant between-group differences, particularly for violent offenders. Altogether violent offenders were more apt to show left-eye preference rather than right-eye preference. As the literature discusses, an increased incidence of left-side preference in a given population may be related to left-hemisphere dysfunction. The finding of a partial correspondence (eye preference only) rather than full correspondence among the three indices of lateral preferences (hand, eye, and foot preferences) may be attributed to environmental influences, such as the effects of brain trauma at birth. In addition, possible associations between hemisphere dysfunction and behavior disorders and crime can also be affected by other biological and social factors over the course of an individual’s development.

Birth Stress and Lateral Preferences

Conflicting evidence exists concerning the possible role of birth stress in the etiology of left-sided lateral preferences. In order to clarify this issue, associations among lateral preferences of hand, eye, and foot and eight indices of prenatal and perinatal stress were examined in the present study on a sample of 987 boys and girls who participated in the Philadelphia Collaborative Perinatal Project. Controls were instituted for some of the methodological and measurement problems encountered in past birth stress and laterality research. Results showed that subjects with different lateral preferences did not differ significantly in their distributions of all but one birth stress items. Hence, there was no substantial evidence for a link between birth stress and left-sided preferences. Alternative hypotheses for the etiology of left-sidedness should therefore be explored.

Directional preferences of bilingual children.

Effects of simultaneous acquisition of differential reading and writing habits (in English and Hebrew) on directional preferences were investigated for 72 bilingual children in Grades 1 to 6. The children reproduced series of single and multiple stimuli; horizontal directions of their responses were recorded. Increased age was accompanied by growing left-right directional preferences in response to all stimuli but Hebrew letters, for which the reversed right-left preferences appeared. These data corroborate previous findings showing effects of reading and writing habits on directional preferences.