Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 196... more Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 1969; Leischner, 1969; Lhermitte and Gautier, 1969) and examinations of epileptic patients using the Wada test (Rasmussen and Milner, 1977) have shown that in almost ail right-handers, the left hemisphere is specialized for language comprehension and expression, both oral and written. However, when normal right-handers are examined on behavioral tasks that are designed to measure asymmetric cerebral functioning (Kimura, 1961, 1963, 1964, 1966), they manifest considerable variability in lateralized verbal performance, a variability that Tzeng and Hung (1985) perceive as a “discrepancy” (p. 124) in relation to the clinical data.
The core of any social structure, from ant to man, is the differentiation of social roles such th... more The core of any social structure, from ant to man, is the differentiation of social roles such that each member of the group contributes his special skills and abilities while receiving from others the benefits of theirs. It is this role differentiation and mutual interdependence that constitute the definition of social organization and that provide for its maintenance, stability, and quality. In the case of the social insects we have a pretty fair understanding of the mechanisms responsible for the critical diversity of roles, but in the case of our own species there has been litde attempt to acquire evidence since, for the most part, the answer has been assumed. Typically man has been viewed as an infinitely plastic clay to be molded at will by social forces, and the diversity of human social roles has been seen as a direct consequence of the social system. Even from the perspective of sociobiology, although the social structure itself is attributed to evolutionary factors, the human infant born into that structure is perceived as having an invariant set of characteristics that define his species identity and that make it possible for him to be conditioned by the extant social forces into any role demanded by the culture. In this view the etiology of human social differentiation is assumed to differ little from that of the social insects. Indeed what we call moral or ethical behavior, or more narrowly "altruistic" behavior, is, as for the insect, a result of kin selection: There is no real altruism, only the selfish gene's attempt to preserve itself. SOCIAL ORGANIZATION AND BEHAVIORAL DIVERSITY The idea that each human being is unique in his skills and propensities, that he seeks to find his own niche where his special abilities Jerre Levy, associate professor of bio psychology
THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: Simplified interpretations of brain function por... more THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: Simplified interpretations of brain function portraying rationality Solely in the left hemisphere and creativity solely in the right are incorrect, but the two sides of the brain do differ in important *
Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 196... more Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 1969; Leischner, 1969; Lhermitte and Gautier, 1969) and examinations of epileptic patients using the Wada test (Rasmussen and Milner, 1977) have shown that in almost ail right-handers, the left hemisphere is specialized for language comprehension and expression, both oral and written. However, when normal right-handers are examined on behavioral tasks that are designed to measure asymmetric cerebral functioning (Kimura, 1961, 1963, 1964, 1966), they manifest considerable variability in lateralized verbal performance, a variability that Tzeng and Hung (1985) perceive as a “discrepancy” (p. 124) in relation to the clinical data.
It is shown that HUDSON'S [1] rejection of the LEVY and NAGYLAKI [2] model for the genetics of ha... more It is shown that HUDSON'S [1] rejection of the LEVY and NAGYLAKI [2] model for the genetics of handedness is predicated on assumptions which contradict well-understood principles of population genetics and on invalid conclusions regarding the nature of the model. It is further demonstrated that the CHAMBERLAIN [3] data are so inconsistent that any reconstruction of them is arbitrary, and that the ANNETT [4] data are unusable for testing the model. IN A RECENT article, HUDSON [1] claimed to retest the genetic model of handedness proposed by LEVY and NAGYLAKI in 1972 [2], and reported that the model's predictions did not fit observations of CHAMBERLAIN [3] and ANNETr [4]. LEVY and NAGYLAKI [2] did not attempt to fit the Chamberlain data because of a number of errors of inconsistency which they found. ANNETT [4] has stated that there is only one error in the Chamberlain data, other than errors of percentages, namely that the number of left-handed sons should be 224 rather than 223. She presents her reconstruction of the Chamberlain observations in her Table 5 [4]. In fact, we do not see where Annett obtained her figures from Chamberlain. He stated quite explicitly that from the original population of 2177 families, there were 9 in which both mothers and fathers were lefthanded and that he obtained 24 additional L x L families through newspaper advertisement. In his Table 2, the first 9 cases represent the original population which produced a total of 25 children, 18 male of whom 4 were left-handed, and 7 female, of whom 3 were left-handed, as Annett displays in her Table 5. However, according to Chamberlain's Table 2, the 24 added families produced a total of 73 children, not 75 as Annett gives, of whom 45 were males, 22 being left-handed, given correctly by Annett, and 28 female (not 30 as Annett gives), of whom 15 (not 17) were left-handed. The last column of Chamberlain's Table 2, representing left-handed females from both the original and added population, sums to 18, not 20 as shown by Chamberlain. Chamberlain states in the body of the text that there were 20 left-handed females from the 33 L x L families, but only shows 18. There is no way of knowing from Chamberlain's data whether there were, in fact, 18 or 20 sinistral girls in his L x L families. However, if we assume that Chamberlain simply omitted two left-handed girls from the 24 added L x L families, Annett's reconstruction fits the figures reported by Chamberlain on pp. 557 and 558 of his article. They do not, however, fit his statements on p. 559. Here, he states that there were only 166 left-handed children from R x R matings. This contrasts with the 308 shown in Annett's table. Taking his number at face value, with a total of 7225 R x R progeny, the percent sinistral offspring is, thus, only 166/7225 = 2"3 ~ (Chamberlain says 2' 1 ~). However, Chamberlain then says that from 2031 R x R families, there were 7714 offspring of whom 270 were left-handed (3-5~). Both of these figures should be contrasted with what Annett displays, 308 sinistral progeny of a total of 7225 produced from R x R matings (4"26~). Chamberlain repeats a second time that R x R matings produced only 2"1 ~o sinistral offspring, and in his penultimate paragraph says that in the original 2177 families, 7807 children were produced, not 7714 as he stated earlier and as Annett shows. As LEVY and NAGYLAKI said in their earlier article [2], the Chamberlain data contain too many inconsistencies, not only of percentages and not only the substitution of 223 sinistral sons of R x R matings instead of 224, but of frequencies as well. In order to reconstruct his observations as Annett claims to have done, one must simply ignore many of the numbers he gives and use those which, for whatever reason, one likes best. In our opinion the Chamberlain paper is totally unusable for constructing genetic models, and we shall, consequently, not discuss it further. HUDSON [1] states that the "problem of differing criteria of handedness (in the Annett study) was felt to be unimportant, as long as the criterion was consistent within a given sample", for testing the Levy and Nagylaki model. He justifies this claim by saying that Levy and Nagylaki would have tested their model
The core of any social structure, from ant to man, is the differentiation of social roles such th... more The core of any social structure, from ant to man, is the differentiation of social roles such that each member of the group contributes his special skills and abilities while receiving from others the benefits of theirs. It is this role differentiation and mutual interdependence that constitute the definition of social organization and that provide for its maintenance, stability, and quality. In the case of the social insects we have a pretty fair understanding of the mechanisms responsible for the critical diversity of roles, but in the case of our own species there has been litde attempt to acquire evidence since, for the most part, the answer has been assumed. Typically man has been viewed as an infinitely plastic clay to be molded at will by social forces, and the diversity of human social roles has been seen as a direct consequence of the social system. Even from the perspective of sociobiology, although the social structure itself is attributed to evolutionary factors, the human infant born into that structure is perceived as having an invariant set of characteristics that define his species identity and that make it possible for him to be conditioned by the extant social forces into any role demanded by the culture. In this view the etiology of human social differentiation is assumed to differ little from that of the social insects. Indeed what we call moral or ethical behavior, or more narrowly "altruistic" behavior, is, as for the insect, a result of kin selection: There is no real altruism, only the selfish gene's attempt to preserve itself. SOCIAL ORGANIZATION AND BEHAVIORAL DIVERSITY The idea that each human being is unique in his skills and propensities, that he seeks to find his own niche where his special abilities Jerre Levy, associate professor of bio psychology
On a simple manual reaction-time (RT) task to lateralized visual signals, right-handers and left-... more On a simple manual reaction-time (RT) task to lateralized visual signals, right-handers and left-handers with the noninverted handwriting posture (RN and LN subjects, respectively) were faster and more consistent when the signal and response hand were homolateral as compared to heterolateral, but left-handers with the inverted handwriting posture (LI subjects) were not. For LI subjects, there was no speed difference for homolateral and heterolateral hand-signal combinations, and there was a clear and significant heterolateral superiority for response consistency. In agreement with suggestions of others, we believe that the anomalous response pattern of LI subjects is likely to be due to a disorder of visuomotor integration and cannot be attributed to reliance on uncrossed motor pathways.
It is proposed that the product-moment correlation between a subject's trial-to-trial performance... more It is proposed that the product-moment correlation between a subject's trial-to-trial performance and sensory half-field in which a stimulus appears be employed as an index of functional differentiation of the cerebral hemispheres, both when reaction time is the dependent variable and when accuracy is the dependent variable. This proposal is based on a model of hemispheric functioning in which the difference in competencies of the two sides of the brain, rather than being a static and unchanging dimension of an individual subject, is seen to vary from moment to moment, a variability that is just as characteristic of the cerebral hemispheres and their relationship as is the mean level of performance for each side. The relative degrees of asymmetry inferred for different subjects differ for laterality indices based on the static assumption versus correlational indices based on the dynamic assumption.
Facial information is processed interactively. Yet, such interactive processing has been examined... more Facial information is processed interactively. Yet, such interactive processing has been examined for discrimination of face parts rather than complete faces. Here we assess interactive processing using a novel paradigm in which subjects discriminate complete faces. Face stimuli, which comprise unilateral facial information (hemifaces) or bilateral facial information from one face (consistent) or two different faces (inconsistent), are shown centrally in a face-matching task. If each half of a complete face is processed independently, accuracy for complete faces can be predicted by the union of accuracies for right and left hemifaces. However, accuracy exceeded this independence prediction for consistent faces (facilitation) and fell below the prediction for inconsistent faces (interference). These effects were reduced or absent for inverted faces. Our findings are consistent with reports of stronger interactive processing for upright than for inverted faces and they quantify effects of interactive processing on the discrimination of complete faces. It is well established that faces are processed by a specialized mechanism that is not used for the processing of most other objects (
Bilateral chimeric stimuli were projected tachistoscopically to split-brain patients for the purp... more Bilateral chimeric stimuli were projected tachistoscopically to split-brain patients for the purpose of assessing hemispheric asymmetries in color-naming, color-matching and memory for colors ofwell-known objects. There was a strong bias for naming colors ofstimuli projected to the left hemisphere, but some patients were also above chance in naming colors of stimuli projected to the right hemisphere. In color-matching tasks, patients varied in the direction and degree of asymmetric control of responses, and asymmetry patterns varied within patients across different tasks, with symmetry of hemispheric control increasing as task complexity increased. Both hemispheres performed well above chance in memory for colors of objects depicted in line-drawings, and the right hemisphere appeared to perform somewhat better than the left.
Perceptual asymmetries for processing chimeric faces were investigated in dextral subjects, rangi... more Perceptual asymmetries for processing chimeric faces were investigated in dextral subjects, ranging in age from 5 years to elderly adults. The task involved deciding which member of a pair of face chimeras presented in free vision looks happier, the one with the smile to the left or its mirror image with the smile to the right (Levy, Heller, Banich, & Burton, 1983a, Brain and Cognition, 2, 404-419). A leftward bias was found for all age groups. However, kindergarteners' mean asymmetry score was lower than that of all other groups combined, most likely due to noise in their data. The direction in which subjects drew circles with their left and right hands was also observed as an index of interhemispheric communication. All groups showed a bias toward drawing the circles in concordant directions except the kindergarteners. The relation between subjects' performance on the circle drawing and facebook tasks is discussed. o 1986 Academic press, hc. Differential right hemisphere involvement in the recognition of faces is supported by studies of patients with unilateral cortical lesions (e.g.,
The influence of lateralized unattended stimuli on the processing of attended stimuli in the oppo... more The influence of lateralized unattended stimuli on the processing of attended stimuli in the opposite visual field can shed light on the nature of information that is transferred between hemispheres. On a cued bilateral task, participants tried to identify a syllable in the attended visual field, which elicits a left hemisphere (LH) advantage and different processing strategies by the two hemispheres. The same or a different syllable or a neutral stimulus appeared in the unattended field. Transmission of unattended syllable codes between hemispheres is symmetric, as revealed by equal interference for the two visual fields. The LH is more accurate than the RH in encoding unattended syllables, as indicated by facilitation in the left but not right visual field and a greater frequency of identifiable intrusions into the left than right field. However, asymmetric encoding strategies are different for attended and unattended syllables.
The asymmetric representation of speech and writing within the dominant, usually left, hemisphere... more The asymmetric representation of speech and writing within the dominant, usually left, hemisphere of the human brain is clearly evident in patients in whom the hemispheres have been surgically separated by midline section of the cerebral commissures (Sperry and Gazzaniga, 1967; Gazzaniga and Sperry, 1967; Gazzaniga, Bogen and Sperry, 1967). Such patients are unable, as a rule, to describe in speech or writing any stimulus information confined exclusively to the subordinate hemisphere, as by presentation to the right nostril (Gordon and Sperry, 1969), left hand, or through the left field of vision (Gazzaniga, Bogen and Sperry, 1963; Geschwind, 1965). So consistent has been this evidence that verbal expression is restricted to the major hemisphere, that the ability to respond correctly with a verbal description has come to be used in many test situations as a criterion of whether a given bit of stimulus information has been received in one or the other hemisphere. The possibility that the minor hemisphere may, nevertheless, possess some latent verbal expression is strongly suggested in studies of aphasia. Patients with destruction of the language centers in the left hemisphere or even with complete left hemispherectomy (Smith, 1966) may still be able to sing, swear, and utter simple familiar words and phrases, including perhaps some minimal propositional speech. In
Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 196... more Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 1969; Leischner, 1969; Lhermitte and Gautier, 1969) and examinations of epileptic patients using the Wada test (Rasmussen and Milner, 1977) have shown that in almost ail right-handers, the left hemisphere is specialized for language comprehension and expression, both oral and written. However, when normal right-handers are examined on behavioral tasks that are designed to measure asymmetric cerebral functioning (Kimura, 1961, 1963, 1964, 1966), they manifest considerable variability in lateralized verbal performance, a variability that Tzeng and Hung (1985) perceive as a “discrepancy” (p. 124) in relation to the clinical data.
The core of any social structure, from ant to man, is the differentiation of social roles such th... more The core of any social structure, from ant to man, is the differentiation of social roles such that each member of the group contributes his special skills and abilities while receiving from others the benefits of theirs. It is this role differentiation and mutual interdependence that constitute the definition of social organization and that provide for its maintenance, stability, and quality. In the case of the social insects we have a pretty fair understanding of the mechanisms responsible for the critical diversity of roles, but in the case of our own species there has been litde attempt to acquire evidence since, for the most part, the answer has been assumed. Typically man has been viewed as an infinitely plastic clay to be molded at will by social forces, and the diversity of human social roles has been seen as a direct consequence of the social system. Even from the perspective of sociobiology, although the social structure itself is attributed to evolutionary factors, the human infant born into that structure is perceived as having an invariant set of characteristics that define his species identity and that make it possible for him to be conditioned by the extant social forces into any role demanded by the culture. In this view the etiology of human social differentiation is assumed to differ little from that of the social insects. Indeed what we call moral or ethical behavior, or more narrowly "altruistic" behavior, is, as for the insect, a result of kin selection: There is no real altruism, only the selfish gene's attempt to preserve itself. SOCIAL ORGANIZATION AND BEHAVIORAL DIVERSITY The idea that each human being is unique in his skills and propensities, that he seeks to find his own niche where his special abilities Jerre Levy, associate professor of bio psychology
THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: Simplified interpretations of brain function por... more THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: Simplified interpretations of brain function portraying rationality Solely in the left hemisphere and creativity solely in the right are incorrect, but the two sides of the brain do differ in important *
Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 196... more Clinical studies of neurological patients with unilateral brain damage (Benson and Geschwind, 1969; Leischner, 1969; Lhermitte and Gautier, 1969) and examinations of epileptic patients using the Wada test (Rasmussen and Milner, 1977) have shown that in almost ail right-handers, the left hemisphere is specialized for language comprehension and expression, both oral and written. However, when normal right-handers are examined on behavioral tasks that are designed to measure asymmetric cerebral functioning (Kimura, 1961, 1963, 1964, 1966), they manifest considerable variability in lateralized verbal performance, a variability that Tzeng and Hung (1985) perceive as a “discrepancy” (p. 124) in relation to the clinical data.
It is shown that HUDSON'S [1] rejection of the LEVY and NAGYLAKI [2] model for the genetics of ha... more It is shown that HUDSON'S [1] rejection of the LEVY and NAGYLAKI [2] model for the genetics of handedness is predicated on assumptions which contradict well-understood principles of population genetics and on invalid conclusions regarding the nature of the model. It is further demonstrated that the CHAMBERLAIN [3] data are so inconsistent that any reconstruction of them is arbitrary, and that the ANNETT [4] data are unusable for testing the model. IN A RECENT article, HUDSON [1] claimed to retest the genetic model of handedness proposed by LEVY and NAGYLAKI in 1972 [2], and reported that the model's predictions did not fit observations of CHAMBERLAIN [3] and ANNETr [4]. LEVY and NAGYLAKI [2] did not attempt to fit the Chamberlain data because of a number of errors of inconsistency which they found. ANNETT [4] has stated that there is only one error in the Chamberlain data, other than errors of percentages, namely that the number of left-handed sons should be 224 rather than 223. She presents her reconstruction of the Chamberlain observations in her Table 5 [4]. In fact, we do not see where Annett obtained her figures from Chamberlain. He stated quite explicitly that from the original population of 2177 families, there were 9 in which both mothers and fathers were lefthanded and that he obtained 24 additional L x L families through newspaper advertisement. In his Table 2, the first 9 cases represent the original population which produced a total of 25 children, 18 male of whom 4 were left-handed, and 7 female, of whom 3 were left-handed, as Annett displays in her Table 5. However, according to Chamberlain's Table 2, the 24 added families produced a total of 73 children, not 75 as Annett gives, of whom 45 were males, 22 being left-handed, given correctly by Annett, and 28 female (not 30 as Annett gives), of whom 15 (not 17) were left-handed. The last column of Chamberlain's Table 2, representing left-handed females from both the original and added population, sums to 18, not 20 as shown by Chamberlain. Chamberlain states in the body of the text that there were 20 left-handed females from the 33 L x L families, but only shows 18. There is no way of knowing from Chamberlain's data whether there were, in fact, 18 or 20 sinistral girls in his L x L families. However, if we assume that Chamberlain simply omitted two left-handed girls from the 24 added L x L families, Annett's reconstruction fits the figures reported by Chamberlain on pp. 557 and 558 of his article. They do not, however, fit his statements on p. 559. Here, he states that there were only 166 left-handed children from R x R matings. This contrasts with the 308 shown in Annett's table. Taking his number at face value, with a total of 7225 R x R progeny, the percent sinistral offspring is, thus, only 166/7225 = 2"3 ~ (Chamberlain says 2' 1 ~). However, Chamberlain then says that from 2031 R x R families, there were 7714 offspring of whom 270 were left-handed (3-5~). Both of these figures should be contrasted with what Annett displays, 308 sinistral progeny of a total of 7225 produced from R x R matings (4"26~). Chamberlain repeats a second time that R x R matings produced only 2"1 ~o sinistral offspring, and in his penultimate paragraph says that in the original 2177 families, 7807 children were produced, not 7714 as he stated earlier and as Annett shows. As LEVY and NAGYLAKI said in their earlier article [2], the Chamberlain data contain too many inconsistencies, not only of percentages and not only the substitution of 223 sinistral sons of R x R matings instead of 224, but of frequencies as well. In order to reconstruct his observations as Annett claims to have done, one must simply ignore many of the numbers he gives and use those which, for whatever reason, one likes best. In our opinion the Chamberlain paper is totally unusable for constructing genetic models, and we shall, consequently, not discuss it further. HUDSON [1] states that the "problem of differing criteria of handedness (in the Annett study) was felt to be unimportant, as long as the criterion was consistent within a given sample", for testing the Levy and Nagylaki model. He justifies this claim by saying that Levy and Nagylaki would have tested their model
The core of any social structure, from ant to man, is the differentiation of social roles such th... more The core of any social structure, from ant to man, is the differentiation of social roles such that each member of the group contributes his special skills and abilities while receiving from others the benefits of theirs. It is this role differentiation and mutual interdependence that constitute the definition of social organization and that provide for its maintenance, stability, and quality. In the case of the social insects we have a pretty fair understanding of the mechanisms responsible for the critical diversity of roles, but in the case of our own species there has been litde attempt to acquire evidence since, for the most part, the answer has been assumed. Typically man has been viewed as an infinitely plastic clay to be molded at will by social forces, and the diversity of human social roles has been seen as a direct consequence of the social system. Even from the perspective of sociobiology, although the social structure itself is attributed to evolutionary factors, the human infant born into that structure is perceived as having an invariant set of characteristics that define his species identity and that make it possible for him to be conditioned by the extant social forces into any role demanded by the culture. In this view the etiology of human social differentiation is assumed to differ little from that of the social insects. Indeed what we call moral or ethical behavior, or more narrowly "altruistic" behavior, is, as for the insect, a result of kin selection: There is no real altruism, only the selfish gene's attempt to preserve itself. SOCIAL ORGANIZATION AND BEHAVIORAL DIVERSITY The idea that each human being is unique in his skills and propensities, that he seeks to find his own niche where his special abilities Jerre Levy, associate professor of bio psychology
On a simple manual reaction-time (RT) task to lateralized visual signals, right-handers and left-... more On a simple manual reaction-time (RT) task to lateralized visual signals, right-handers and left-handers with the noninverted handwriting posture (RN and LN subjects, respectively) were faster and more consistent when the signal and response hand were homolateral as compared to heterolateral, but left-handers with the inverted handwriting posture (LI subjects) were not. For LI subjects, there was no speed difference for homolateral and heterolateral hand-signal combinations, and there was a clear and significant heterolateral superiority for response consistency. In agreement with suggestions of others, we believe that the anomalous response pattern of LI subjects is likely to be due to a disorder of visuomotor integration and cannot be attributed to reliance on uncrossed motor pathways.
It is proposed that the product-moment correlation between a subject's trial-to-trial performance... more It is proposed that the product-moment correlation between a subject's trial-to-trial performance and sensory half-field in which a stimulus appears be employed as an index of functional differentiation of the cerebral hemispheres, both when reaction time is the dependent variable and when accuracy is the dependent variable. This proposal is based on a model of hemispheric functioning in which the difference in competencies of the two sides of the brain, rather than being a static and unchanging dimension of an individual subject, is seen to vary from moment to moment, a variability that is just as characteristic of the cerebral hemispheres and their relationship as is the mean level of performance for each side. The relative degrees of asymmetry inferred for different subjects differ for laterality indices based on the static assumption versus correlational indices based on the dynamic assumption.
Facial information is processed interactively. Yet, such interactive processing has been examined... more Facial information is processed interactively. Yet, such interactive processing has been examined for discrimination of face parts rather than complete faces. Here we assess interactive processing using a novel paradigm in which subjects discriminate complete faces. Face stimuli, which comprise unilateral facial information (hemifaces) or bilateral facial information from one face (consistent) or two different faces (inconsistent), are shown centrally in a face-matching task. If each half of a complete face is processed independently, accuracy for complete faces can be predicted by the union of accuracies for right and left hemifaces. However, accuracy exceeded this independence prediction for consistent faces (facilitation) and fell below the prediction for inconsistent faces (interference). These effects were reduced or absent for inverted faces. Our findings are consistent with reports of stronger interactive processing for upright than for inverted faces and they quantify effects of interactive processing on the discrimination of complete faces. It is well established that faces are processed by a specialized mechanism that is not used for the processing of most other objects (
Bilateral chimeric stimuli were projected tachistoscopically to split-brain patients for the purp... more Bilateral chimeric stimuli were projected tachistoscopically to split-brain patients for the purpose of assessing hemispheric asymmetries in color-naming, color-matching and memory for colors ofwell-known objects. There was a strong bias for naming colors ofstimuli projected to the left hemisphere, but some patients were also above chance in naming colors of stimuli projected to the right hemisphere. In color-matching tasks, patients varied in the direction and degree of asymmetric control of responses, and asymmetry patterns varied within patients across different tasks, with symmetry of hemispheric control increasing as task complexity increased. Both hemispheres performed well above chance in memory for colors of objects depicted in line-drawings, and the right hemisphere appeared to perform somewhat better than the left.
Perceptual asymmetries for processing chimeric faces were investigated in dextral subjects, rangi... more Perceptual asymmetries for processing chimeric faces were investigated in dextral subjects, ranging in age from 5 years to elderly adults. The task involved deciding which member of a pair of face chimeras presented in free vision looks happier, the one with the smile to the left or its mirror image with the smile to the right (Levy, Heller, Banich, & Burton, 1983a, Brain and Cognition, 2, 404-419). A leftward bias was found for all age groups. However, kindergarteners' mean asymmetry score was lower than that of all other groups combined, most likely due to noise in their data. The direction in which subjects drew circles with their left and right hands was also observed as an index of interhemispheric communication. All groups showed a bias toward drawing the circles in concordant directions except the kindergarteners. The relation between subjects' performance on the circle drawing and facebook tasks is discussed. o 1986 Academic press, hc. Differential right hemisphere involvement in the recognition of faces is supported by studies of patients with unilateral cortical lesions (e.g.,
The influence of lateralized unattended stimuli on the processing of attended stimuli in the oppo... more The influence of lateralized unattended stimuli on the processing of attended stimuli in the opposite visual field can shed light on the nature of information that is transferred between hemispheres. On a cued bilateral task, participants tried to identify a syllable in the attended visual field, which elicits a left hemisphere (LH) advantage and different processing strategies by the two hemispheres. The same or a different syllable or a neutral stimulus appeared in the unattended field. Transmission of unattended syllable codes between hemispheres is symmetric, as revealed by equal interference for the two visual fields. The LH is more accurate than the RH in encoding unattended syllables, as indicated by facilitation in the left but not right visual field and a greater frequency of identifiable intrusions into the left than right field. However, asymmetric encoding strategies are different for attended and unattended syllables.
The asymmetric representation of speech and writing within the dominant, usually left, hemisphere... more The asymmetric representation of speech and writing within the dominant, usually left, hemisphere of the human brain is clearly evident in patients in whom the hemispheres have been surgically separated by midline section of the cerebral commissures (Sperry and Gazzaniga, 1967; Gazzaniga and Sperry, 1967; Gazzaniga, Bogen and Sperry, 1967). Such patients are unable, as a rule, to describe in speech or writing any stimulus information confined exclusively to the subordinate hemisphere, as by presentation to the right nostril (Gordon and Sperry, 1969), left hand, or through the left field of vision (Gazzaniga, Bogen and Sperry, 1963; Geschwind, 1965). So consistent has been this evidence that verbal expression is restricted to the major hemisphere, that the ability to respond correctly with a verbal description has come to be used in many test situations as a criterion of whether a given bit of stimulus information has been received in one or the other hemisphere. The possibility that the minor hemisphere may, nevertheless, possess some latent verbal expression is strongly suggested in studies of aphasia. Patients with destruction of the language centers in the left hemisphere or even with complete left hemispherectomy (Smith, 1966) may still be able to sing, swear, and utter simple familiar words and phrases, including perhaps some minimal propositional speech. In
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