Body asymmetry affects conjugate lateral eye movement

A. H. Baker (1989) and A. H. Baker and A. I. Ledner (1990) reported that asymmetrical visual stimulation affects conjugate lateral eye movement (CLEM). In the present article, the authors explored whether asymmetrical body position similarly affects CLEM. The authors assessed CLEMs twice in a counterbalanced design. In the control (symmetric) condition, each participant sat in a completely symmetrical position facing a wall devoid of any asymmetrical features. In the experimental (asymmetrical) condition, half the participants rotated their heads 68 degrees clockwise relative to their bodies to face the experimenter, and the other half rotated their heads 68 degrees counterclockwise, also to face the experimenter. CLEM was predominantly toward the body's position in the asymmetrical condition rather than toward the body's position in the symmetrical condition.     

Dichotic ear preferences of stuttering children and adults.

39 stutterers and 39 normal speakers indicated their ear preferences for dichotically presented words and digits. A single response mode for both dichotic words and digits was selected to study speech perception. Stutterers showed significantly less of the normal right-ear preference for dichotic words and digits than non-stutterers. The proportion of stutterers who failed to demonstrate a right-ear preference for dichotic words was significantly greater than for non-stutterers. 18% of the stutterers and none of the non-stutterers showed reversed or a left-ear preference for dichotic digits. Although non-stuttering children and adults performed alike on the dichotic tasks, the right-ear dichotic-words scores of stuttering children were significantly smaller than those of adult stutterers. The results are related to an early notion that stuttering may be related to mixed dominance and recent evidence showing that large percentages of older stuttering children show spontaneous remission of stuttering.     

Dichotic listening ear asymmetry: Patterns of longitudinal development

Dichotic listening research with children has continued to be prevalent although numerous authors have described both theoretical and methodological limitations with traditional dichotic listening free-recall paradigms. The present research adds to this growing skepticism by reanalyzing two major longitudinal studies of children's ear asymmetries. These two studies, based in different countries (United States, Holland), utilized highly similar paradigms (free-recall digits), subjects (males), and age levels (kindergarten and second and fifth grade). The questions of ear advantage development, patterns of ear advantages, and the relationship between dichotic listening performance and reading skills are addressed from the multiple statistical methodologies represented in the literature. From these analyses, support for all of the major hypotheses regarding the developmental patterns of dichotic listening performances could be obtained from the same data samples. The use of traditional free-recall dichotic listening paradigms are not recommended for use with children. The implications for future research are discussed.     

The left: lateral eye movements and ideology.

The lateral eye movements of 24 college students were videotaped as they reflected on spatial and analytical questions. As predicted, participants with more initial movements to the left had significantly higher scores on the leftist (or humanistic) index of the Tomkin's Polarity Scale. The direction of this relationship was reversed for the rightist index (right movers scoring higher) but this difference was not significant. Results are interpreted as additions to evidence which suggests a connection between the left and right sides of the human body and more global dichotomies of ideology or personality.     

Easier done than undone: asymmetry in the malleability of implicit preferences

Dual-process models imply that automatic attitudes should be less flexible than their self-reported counterparts; the relevant empirical record, however, is mixed. To advance the debate, the authors conducted 4 experiments investigating how readily automatic preferences for one imagined social group over another could be induced or reversed. Experiments 1 and 2 revealed that automatic preferences, like self-reported ones, could be readily induced by both abstract supposition and concrete learning. In contrast, Experiments 3 and 4 revealed that newly formed automatic preferences, unlike self-reported ones, could not be readily reversed by either abstract supposition or concrete learning. Thus, the relative inflexibility of implicit attitudes appears to entail, not immunity to sophisticated cognition, nor resistance to swift formation, but insensitivity to modification once formed.     

Variations in patterns of lateral asymmetry among dextrals

Evidence supporting individual variations in patterns of hemispheric involvement in the recognition of visuo-spatial and verbal stimuli among dextrals is reported. In Experiment 1, subjects' asymmetry scores on a task that was nonlateralized for the group as a whole were significantly correlated with their asymmetry scores on right-hemisphere-specialized tasks, including face recognition. In Experiment 2, subjects' asymmetry scores on a task that was nonlateralized for the group as a whole were significantly correlated with their asymmetry scores on a left-hemisphere-specialized word recognition task. These results suggest that individual dextrals' asymmetry scores on lateralized tasks are a joint function of a subject's underlying hemispheric specialization for that task and stable individual variations in asymmetric hemispheric reliance.     

Relations among hand preference,craniofacial asymmetry,and ear advantage in young subjects

The relations for hand preference with craniofacial asymmetry and ear advantage, and between craniofacial asymmetry and ear advantage were investigated in young healthy subjects. Ear advantage was recorded as duration of hearing, craniofacial asymmetry by computerized tomography in 44 right-handed and 38 left-handed male and female high school students. Right-handers had a right ear advantage and a larger left craniofacial region, whereas left-handers had a left ear advantage and a larger right craniofacial region. These results are consistent with the speculation that hand preference may be related to craniofacial and consequently aural asymmetries.     

Automatic attention lateral asymmetry in visual discrimination tasks

There is evidence that automatic visual attention favors the right side. This study investigated whether this lateral asymmetry interacts with the right hemisphere dominance for visual location processing and left hemisphere dominance for visual shape processing. Volunteers were tested in a location discrimination task and a shape discrimination task. The target stimuli (S2) could occur in the left or right hemifield. They were preceded by an ipsilateral, contralateral or bilateral prime stimulus (S1). The attentional effect produced by the right S1 was larger than that produced by the left S1. This lateral asymmetry was similar between the two tasks suggesting that the hemispheric asymmetries of visual mechanisms do not contribute to it. The finding that it was basically due to a longer reaction time to the left S2 than to the right S2 for the contralateral S1 condition suggests that the inhibitory component of attention is laterally asymmetric.     

Relationship between birth order, birth stress, and lateral preferences: a critical review

Reviews the literature examining the relationship between birth order, birth stress, and lateral preferences in nonclinical samples, with special emphasis on reports since 1971. The review found no evidence to relate birth order position to deviations from right-sidedness for either sex. More direct measures of birth stress indicated that deviations from right-handedness (particularly for male subjects), and also right-eyedness, were statistically related to specific birth stressors. It should be stressed, however, that all the relationships, including the significant ones, were very weak, accounting for less than 1% of the variance. When statistical significance was achieved, it was largely due to the huge sample sizes used in the meta-analyses. Methological and theoretical problems exist in the current literature, and we offer some suggestions to resolve them.     

The asymmetry of lateral interference in visual letter identification

Asymmetry of masking refers to the fact that a masking letter placed on the peripheral side of a target in the visual field will interfere more with recognition of the target than will a masking letter placed on the central side of the target. The experiments in this paper show that lateral masking for a pair consisting of a single target and a single mask cannot be entirely explained by processing interference caused by the mask but that masking ]has a component of purely sensory interference. Furthermore, the asymmetry of masking at the sensory level, when all sources of processing interference are eliminated, can be explained in terms of the falloff in acuity from the center to the periphery of the retina. The sensory component of masking is asymmetrical because, with the target at a constant retinal location, the target-plus-mask configuration is, as a whole, more peripherally located with a peripheral mask than a central one, and it is the location of the target-plus-mask configuration that determines performance.     

Effects of level of arousal and type of task on bilateral skin conductance asymmetry and conjugate lateral eye movements

Several recent studies have indicated that the degree and direction of bilateral skin conductance (BSC) asymmetry and the direction of conjugate lateral eye movements (CLEMs) both index hemispheric functioning. Evidence also suggests that BSC asymmetry decreases and CLEMs become more unidirectional as level of arousal increases. Thirty-two normal adults received an habituation series of five-second tones followed by 40 questions. All stimuli were tape recorded. The questions (Schwartz, Davidson, and Maer, 1975) were grouped in four series: 10 verbal-emotional, 10 verbalnonemotional, 10 spatial-emotional, and 10 spatial-nonemotional. The order in which the four series were presented was counterbalanced across subjects. Prior to each question, subjects fixated the face of a mannequin. Sixteen subjects (high arousal) had five seconds to contemplate their answer; the remaining 16 (low arousal) had 10 seconds. Instructions for the high arousal group specified that intelligence and problem-solving ability was being tested, and that speed and accuracy were very important. Those for the low arousal group indicated casually that subjects were to ponder a series of questions. BSC levels, SC response amplitudes, and CLEMs were measured during a five-second interval following each tone or question. BSC levels were greater under the High Arousal condition. While approximately two-thirds of the subjects showed BSC asymmetry (roughly evenly divided between those with larger left and right hand responses), neither the degree nor direction of the asymmetries changed as a function of question type. While CLEM direction was more sensitive to question type under low arousal, (i.e., verbal questions resulted in predominantly right-going CLEMs and spatial questions resulted in predominantly left-going CLEMs) they tended to be stereotyped (i.e., unidirectional) under high arousal. Finally, no relationship was observed between CLEM direction and BSC asymmetry under either high or low arousal condition.     

Search asymmetry and eye movements in infants and adults

Search asymmetry is characterized by the detection of a feature-present target amidst feature-absent distractors being efficient and unaffected by the number of distractors, whereas detection of a feature-absent target amidst feature-present distractors is typically inefficient and affected by the number of distractors. Although studies have attempted to investigate this phenomenon with infants (e.g., Adler, Inslicht, Rovee-Collier, & Gerhardstein in Infant Behavioral Development, 21, 253–272, 1998; Colombo, Mitchell, Coldren, & Atwater in Journal of Experimental Psychology: Learning, Memory and Cognition, 19, 98–109, 1990), due to methodological limitations, their findings have been unable to definitively establish the development of visual search mechanisms in infants. The present study assessed eye movements as a means to examine an asymmetry in responding to feature-present versus feature-absent targets in 3-month-olds, relative to adults. Saccade latencies to localize a target (or a distractor, as in the homogeneous conditions) were measured as infants and adults randomly viewed feature-present (R among Ps), feature-absent (P among Rs), and homogeneous (either all Rs or all Ps) arrays at set sizes of 1, 3, 5, and 8. Results indicated that neither infants’ nor adults’ saccade latencies to localize the target in the feature-present arrays were affected by increasing set sizes, suggesting that localization of the target was efficient. In contrast, saccade latencies to localize the target in the feature-absent arrays increased with increasing set sizes for both infants and adults, suggesting an inefficient localization. These findings indicate that infants exhibit an asymmetry consistent with that found with adults, providing support for functional bottom-up selective attention mechanisms in early infancy.     

Digit ratio (2D:4D), lateral preferences, and performance in fencing

The second to fourth digit ratio (2D:4D) is a sexually dimorphic trait (men tend to have lower values than women) and a likely biomarker for the organizational (permanent) effects of prenatal androgens on the human brain and body. Prenatal testosterone, as reflected by 2D:4D, has many extragenital effects, including its relevance for the formation of an efficient cardiovascular system. Previous research, reviewed here, has therefore investigated possible associations of 2D:4D with sport performance. Several studies found more masculinized digit ratio patterns (low 2D:4D values or a negative right-minus-left difference in 2D:4D) to be related to high performance in running, soccer, and skiing. The present research tested this hypothesis in a sample of 54 tournament fencers, predominantly from Austria. For men, negative right-left differences in 2D:4D corresponded significantly to better current as well as highest national fencing rankings, independent of training intensity and fencing experience. The mean 2D:4D values of these fencers were significantly lower and the proportion of left-handers was elevated relative to the local general population. For the right hand, the ratio was somewhat lower in male sabre fencers than in male epée and foil fencers combined and significantly lower in left-handed compared to right-handed fencers. Although nonsignificant due to low statistical power, effect sizes suggested that crossed versus congruent hand-eye and hand-foot preferences might also be related to fencing performance. The present findings add to the evidence that 2D:4D might be a performance indicator for men across a variety of sports.     

Hemispheric dominance, dichotic listening and lateral eye movement behaviour

Abstract.— Because lateral corrective eye movements have been shown to influence the results of the dichotic listening test, it was supposed that differences in the scoring on this test by right and left eye movers could be found. Only in the entire group of 22 right handed subjects and in the subgroup of 8 right eye movers a significant right ear superiority was found. In the left mover group (14 subjects) right ear superiority in dichotic listening was not significant. These results are interpreted in terms of possible interhemispheric differences in the level of "activity", facilitating or hampering perception of verbal material in the contralateral ear.     

Development of lateral asymmetry in the perception of sequentially touched fingers

In order to investigate lateral asymmetry in tactile perception, two or four fingers of normal primary school children were touched sequentially. Stimulation was either unimanual or bimanual and either verbal or nonverbal responses were required. Right hand advantage was demonstrated subsequent to uni- and bimanual stimulation in both the verbal and nonverbal response conditions. Neither an age nor a sex effect on laterality was found. Right hand advantage was affected by direction of stimulation in the bimanual condition. Left hemispheric dominance was argued to be related to the temporal nature of the tasks.     

Conjugate lateral eye movements as an index of hemispheric activation.

Right handers moved their eyes leftward when solving spatial problems and rightward for verbal problems when the questioner sat behind them. When facing the questioner, the same subjects moved their eyes predominantly in only one direction, either right or left, regardless of problem type. The results indicate that the cerebral hemispheres, though specialized for problem type, are also preferentially activated within the same individuals.     

Multiplication by eye and by ear for Chinese-speaking and English-speaking adults.

English-speaking (n = 32) and Chinese-speaking adults (n = 32) solved single-digit multiplication problems. In one condition, problems were presented as visual digits (e.g., 8 x 9). In the other condition, problems were presented as auditory number words in the participant's first language (e.g., /eit/ /taimz/ /nain/). Chinese-speaking adults made proportionately more operand-intrusion errors (e.g., 4 x 8 = 24) than English-speaking adults. Both groups made more operand-intrusion errors with auditory than with visual presentation. These findings are similar to those found when participants solve problems presented as visual number words (e.g., eight x nine), suggesting that in both cases the activation of phonological codes interferes with processing.