Left Hemisphere Advantage Research Articles

Processing of form stimuli presented unilaterally in humans, chimpanzees (Pan troglodytes), and monkeys (Macaca mulatta).

Visual forms were unilaterally presented using a video-task paradigm to 10 humans, 3 chimpanzees, and 2 rhesus monkeys to determine whether hemispheric advantages existed in the processing of these stimuli. Both accuracy and reaction time served as dependent measures. For the chimpanzees, a significant right hemisphere advantage was found within the first 3 test sessions. The humans and monkeys failed to show a hemispheric advantage as determined by accuracy scores. Analysis of reaction time data revealed a significant left hemisphere advantage for the monkeys. A Visual Half-Field x Block interaction was found for the chimpanzees, with a significant left visual field advantage in Block 2, whereas a right visual field advantage was found in Block 4. In the human subjects, a left visual field advantage was found in Block 3 when they used their right hands to respond. The results are discussed in relation to recent reports of hemispheric advantages for nonhuman primates.

Hemispheric Memory for Surrealistic Versus Realistic Paintings

The issue of hemispheric processing of art works, either alone or in relation to a certain aspect of language was investigated in normal subjects. Three experiments were performed. In the first, memory for surrealistic versus realistic pictures was investigated. In the second, memory for metaphoric versus literal titles of these pictures was measured. In the third, memory for the paintings was determined as a function of the same titles. The results of the first experiment showed a right visual field (RVF) advantage for the surrealistic pictures. No field difference emerged for the realistic pictures. The results of the second experiment indicated a RVF advantage in memory for metaphoric titles. Moreover, in the RVF, there was an advantage for titles from surrealistic-metaphoric pairs over all other pairings. Results of experiment three showed a RVF advantage in remembering pictures from surrealistic-metaphoric pairs and, in the left visual field (LVF) there was advantage for pictures with literal titles. Taken together, the results suggest left hemisphere advantage in processing meaningful, yet incongruous arrays, both pictorial and linguistic. The results are discussed in terms of hemispheric memory for art works, metaphors, and the relationship between the two in the brain.

Hemispheric Differences in Odour Recognition

Two experiments were designed in order to study hemispheric differences in odour recognition in normal subject. In the first experiment subjects first smelled an odour and then a visual stimulus (a picture or a word related or unrelated to the odour) was flashed eitherto the left or to the right hemisphere for 150 milliseconds. Subjects had to press a key if the two stimuli (olfactory and visual) matched and another key if they did not. Reaction time analysis showed that the responses were faster when the second stimulus (either picture or word) was presented to the right hemisphere. In a second experiment the first stimulus was auditory rather than olfactory. Subjects were instructed to listen to names of odorants and then to respond to pictures or written names as in the first experiment. In this case a left hemisphere advantage emerged, presumably related to the priming of the left hemisphere by the auditorially presented verbal stimulus.

Cerebral lateralization of language in deaf and hearing people

In Experiment 1 neither hearing nor prelingually deaf signing adolescents showed marked lateralization for lexical decision but, unlike the hearing, the deaf were not impaired by the introduction of pseudohomophones. In Experiment 2 semantic categorization produced a left hemisphere advantage in the hearing for words but not pictures whereas in the deaf words and signs but not pictures showed a right hemisphere advantage. In Experiment 3 the lexical decision and semantic categorization findings were confirmed and both groups showed a right hemisphere advantage for a face/nonface decision task. The possible effect of initial language acquisition on the development of hemispheric lateralization for language is discussed.

Associations of Timing of Puberty, Spatial Ability, and Lateralization in Adult Women

The purpose of this study was to determine whether timing of puberty is related to spatial ability in adult women, and whether, if so, the relation could be attributed to timing-related differences in hemispheric specialization and/or timing-related differences in personality and spatial activity. 53 female undergraduates were given 2 tests of spatial ability, tests of both right-hemispheric and left-hemispheric specialization using tachistoscopic procedures, several tests assessing masculinity and femininity, and a questionnaire on spatial activity. They were also asked to recall their age at menarche. Later age at menarche was associated with greater right-hemispheric advantage on the dot location task but not with higher spatial ability. Spatial ability in this sample was in fact correlated with greater left-hemispheric advantage on the dot location task, as well as with more balanced hemispheric specialization on the syllable task. It is suggested that variability in findings regarding cognitive correlates of timing of puberty may be related to variability in strategies for approaching tasks. The implications of these data for efforts to explain sex-related differences in spatial ability are discussed.

Mental rotation in a commissurotomized subject

The commissurotomized subject L.B. showed a strong right-hemispheric advantage on a task requiring him to judge rotated letters normal or backward, but a left-hemispheric advantage in a task requiring discrimination of the same letters, implying that the right-hemispheric advantage has to do with mental rotation. However, his right hemisphere proved unable to perform a task requiring mental rotation of a simple unfamiliar pattern to a designated “upright”, and was inferior to the left on a task requiring two such patterns, at varying orientations relative to one another, to be judged same or different. We suggest that the deficiency of the right hemisphere on these tasks was unrelated to mental rotation per se, but reflected a failure to comprehend the tasksproperly.

Cerebral lateralization of Chinese-English bilingual functions

There is evidence that auditory reception of the second language of bilinguals is less lateralized in the left hemisphere, when the two languages involved are more dissimilar, such as Chinese and English. The present study shows, with a test of simultaneous finger tapping and backward counting as well as a test of tachistoscopic bilateral presentation, that this differential lateralization does not apply to non-auditory functions, and both Chinese and English showed a left hemisphere advantage. Bilateral presentation of bilingual words produced greatest interference, when compared with bilateral presentation of unilingual words, or bilateral presentation of words and numbers.

Influence des conditions de présentation sur les asymétries hémisphériques dans une tâche de comparaison de formes

Summary : Influence of the presentation conditions on hemispherie asymmetries in a form comparison task. The purpose of the present experiment was to examine the influence of the presentation conditions on the emergence of hemispherie asymmetries. Four groups were subjected to laterally presented meaningful and meaningless forms in a « same » / « different » judgment task concerning the orientation of the stimuli to be compared. The results show an interaction between the experimental conditions, determined by the duration of exposure, long (L) or short (C) of the reference stimulus and the presence (I) or absence (I) of an interstimulus interval (ISI), and the visual field of presentation. A short duration of exposure without ISI (CI condition) resulted in an advantage of the right hemisphere (RH) for « same » judgments. The increase of the presentation time (Ll condition) maintained the RH advantage but this time for « different » judgments. Additional processing time provided by the introduction of an ISI (LI condition) benefited more the left hemisphere (LH) than the RH. This condition led to a disappearance of laterality effects. Finally, the introduction of an ISI just after a brief presentation time (CI condition) degraded the performance. This degradation affected the early processed components of the visual display. This condition gave rise to a LH advantage. Reaction times were shorter for the meaningful than for the meaningless stimuli but no interaction was found between this factor and the visual field of presentation. The results are interpreted in terms of hemispheric asymmetries for global/local information processing. Key words : hemispheric asymmetries, form perception, global/local information processing.

Gestalt laws of perceptual organization in an embedded figures task: Evidence for hemispheric specialization

An embedded figures task was used to investigate hemispheric specialization for visual parsing. Error data from 40 normal right-handed males revealed a right-hemisphere advantage for parsing governed by the Gestalt laws of organization. In contrast, for parsing that violated those laws, subjects who could perform such parsing at better-than-chance levels showed a left-hemisphere advantage. A simple left hemisphere/analytic, right hemisphere/holistic dichotomy is too ambiguous to account for the results, because it fails to specify the level of visual structure (e.g. whole figures, intermediate components, or elementary segments) that is to be taken as a reference point for defining particular tasks as analytic or holistic; what is analytic from one point of view is holistic from another. We focus instead on principles of perceptual organization that characterize the results of perceptual processing, regardless of whether those results are seen as the outcome of analytic or holistic processing.

Patterns of lateralization and performance levels for verbal and spatial tasks in congenital androgen deficiency

The effects of congenital deficiency of gonadal hormones on verbal and spatial performance and on the establishment of hemispheric asymmetries were investigated in a group of patients with idiopathic hypogonadotropic hypogonadism. The patients showed a left hemispheric advantage for verbal material and were mildly impaired, mainly on tasks involving a short-term memory load, in comparison with a matched control group. These results do not indicate a specific role of gonadal hormones on the establishment of hemispheric asymmetries. Lack of exposure during brain development results in a decrease in memory functions which is not specific for verbal or spatial material.

Visual field differences in the processing of numerical stimuli

Twenty-four right-handed subjects received random presentations of the numbers 1–6 in the form of words, digits, and dot patterns, to the left and right visual fields. Accuracy and reaction time were recorded for an odd-even judgment requiring a manual response. A significant stimulus type of visual field interaction was obtained, with words showing a left-hemisphere advantage and digits and dot patterns showing a right-hemisphere advantage. This pattern supports Coltheart's 1980Deep dyslexia: A right hemisphere hypothesis, In M. Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia, London: Routledge & Kegan Paul) right hemisphere reading hypothesis, which suggests that the left hemisphere's general advantage in processing linguistic material may be specific to stimuli which involve phonological processing. When phonological processing is not possible (e.g., for arabic digits and other ideographic orthographies), the right hemisphere may have an advantage because of its superior visuospatial processing capabilities.

RELATIVE VS ABSOLUTE RIGHT HEMISPHERE SUPERIORITY FROM LATERAL DIFFERENCES IN VISUAL PROCESSING BY NORMALS: AN EXAMPLE OF UNCERTAINTY IN EXPERIMENTAL NEUROPSYCHOLOGY

Statistical tools (correlations and analyses of variance) have been proposed to decide whether a hemispheric functional asymmetry reflects absolute or relative cerebral superiority. A set of 16 normal subjects were given two tasks involving right hemisphere competences in the visual modality: the recognition of a small set of easily discriminated faces and meaningless geometrical figures, displayed in the lateral visual fields. The statistical tools did not perfectly agree with one another as had already been noted in a previous study. The results also showed a left hemisphere advantage, contrary to expectations; this last observation is linked with a possible asymmetrical effect of familiarization with the material

Left hemisphere advantage in the mouse brain for recognizing ultrasonic communication calls.

In humans, sound perceived as speech is processed preferentially by the right ear and the left hemisphere of the brain. Among animals, such an advantage of one hemisphere (lateralization) in processing communication sound from other members of the species has so far been demonstrated only in macaque monkeys. I report here that in the house mouse, which has a very much less elaborate forebrain than man or macaque monkey, the ultrasonic calls that are emitted by young mice to evoke maternal caring behavior are preferentially recognized by the left hemisphere. In females with no experience of pups, which have been trained to respond to the same ultrasonic calls by conditioning, no advantage for one hemisphere is detected. The results suggest that lateralization of this function evolved early in mammals and emphasize that an innate predisposition for perceiving communication sounds is connected with a left-hemisphere advantage in processing them. This experimental system is a readily-available animal model for studying lateralized auditory brain functions.

Confusion and visual field effects in rhyme and name letter matching.

Recent evidence (Boles & Eveland, 1983) suggests that mixed-case letter pairs such asAa are matched not through a common phonetic or name code, but rather through the detection of visual equivalence between alternate letter cases. The generation model states that equivalence is detected by internally generating the opposite cases of the letters, which are then compared to the stimulus pair trace. What is lacking in this formulation, however, is evidence that the phonetic or name code can be used for other letter-matching tasks and that it has a predominantly left-hemisphere lateralization. Here eight experiments employed rhyme- and name-matching tasks along with manipulations of phonetic and generation confusion. Meta-analysis of the reaction time and error results shows the expected interaction of task and type of confusion. In addition, a small right visual field or left hemisphere advantage was found for rhyme matches, but not for name matches. It is concluded on both confusion and lateralization grounds that rhyme- and name-matching tasks employ different processes, and that these can be described, respectively, as phonetic and visual in nature.

Laterality and School Achievement: Interactions between Familial Handedness and Assessed Laterality

179 8- to 12-yr.-old children received hand-preference, eye-preference, dichotic (digits and nonverbal sounds) tests, and the Wide Range Achievement Test. These data and those from previous studies suggest that brain organization for receptive language laterality can be predicted by familial handedness in conjunction with assessed hand-eye preference. A model of optimum functional ear laterality patterns within a given brain organization is advanced. For example, the "typical" pattern of a right-ear (left-hemisphere) advantage for verbal stimuli was associated with high achievement scores only for right-handed individuals with a family history of dextrality.

Lateralization effects in reading pointed and unpointed Hebrew.

Hebrew has two forms of spelling, pointed and unpointed. In the pointed spelling, diacritical signs (pointing) are added to consonantal letters to convey vowel information. These are omitted in the unpointed spelling. Since pointing conveys information that is critical for the prelexical derivation of phonology, it was hypothesized that its absence would prove detrimental for left hemisphere (LH) but not for right hemisphere (RH) reading and that, for the former, pointing effects would increase with increasing word length. Three experiments, one involving lexical decision and two involving word pronunciation, yielded little support for these hypotheses; rather, pointing had an overall adverse effect on performance, and this effect tended to be more pronounced for LH reading. In general, however, the results indicated an LH advantage. Since for central vision pointing has been found to aid performance under similar conditions, the results were seen to suggest a distinction between the visual and the phonological effects of pointing: pointing may impair early stages of visual analysis but may aid in the derivation of speech codes.

Lateralized processes in face recognition.

In this paper a model is presented in which face recognition is analysed into several stages, each of which may be independently lateralized. Evidence is reviewed which suggests that lateralization is important at all stages of processing a face. Early visuospatial processing, and the creation and comparison of facial representations, appear to be carried out more efficiently by the right hemisphere. Comparisons based on discrete, namable features of faces may yield a left hemisphere advantage. It is also proposed that faces may activate semantic information, including names, more efficiently in the left hemisphere. The model is useful in resolving inconsistencies in the degree and direction of asymmetries found in face-recognition tasks. Suggestions are also made for future research.

Do Individuals with Down's Syndrome Possess Right Hemisphere Language Dominance?

A dichotic digits task with selective listening and attention-switching instructions, was administered to 10 mentally retarded individuals with Down's Syndrome between the ages of 10 and 37 years. Attention was focused on one ear for 20 trials before switching attention to the opposite ear after a 5-minute interval. A majority displayed a right ear-left hemisphere advantage for correct responses, although this advantage failed to reach significance. Comparison of left and right ear intrusion errors when each ear was attended first showed significantly more intrusions from the unattended right ear. No priming effects were found. The results do not support the hemispheric reversed specialization hypothesis. Rather, it is suggested that while Down's Syndrome individuals do possess an inherent left hemisphere advantage for language, such individuals may suffer from a left hemisphere information processing disorder that can produce functional reversals in dichotic listening.

Cerebral asymmetry in congenitally deaf subjects

Congenitally deaf subjects exposed to tachistoscopic presentation of English words, British Sign Language (BSL) signs, manual letters stimuli and a non-verbal task showed a left hemisphere advantage for English words and signs, a right hemisphere advantage for manual letters and no field differences for the non-verbal task.

Hemispheric differences for semantically and phonologically primed nouns: A tachistoscopic study in normals

Normal individuals performed two matching tasks. In one task, semantic processing, synonyms had to be recognized. Half the stimuli were picturable and half were nonpicturable nouns. In this task, recognition of picturable synonyms was found to have hemifield symmetry, whereas recognition of nonpicturable synonyms yielded a left-hemisphere superiority, indicating that semantic matching itself did not reveal equal performance of both hemispheres. It is concluded that picturable synonyms might be recognized either by processes of visual imagery, which pertain to right-hemisphere function, or by their phonological or phonic features, which are processed by the left hemisphere. The other task, shown in previous research to exhibit a left-hemisphere superiority, was to decide if two nouns (homophones) were equally pronounced. Here a distinct left-hemisphere advantage was revealed.