Multitask investigation of individual differences in hemispheric asymmetry

Right-handed subjects (N = 120) participated in four different laterality tasks designed to measure aspects of cerebral hemisphere asymmetry: identification of dichotically presented consonant-vowel syllables (CVs), examination of the effects of concurrent repetition of CVs and concurrent anagram solution on finger-tapping by the right and left hands, lateralized identification of CVs presented tachistoscopically to the left and right visual fields, and left/right biases on a free-vision face task involving judgments of emotion. Ear differences in the dichotic listening task were related to the pattern of lateralized interference in the dual-task finger-tapping paradigm. There were no other significant relations between pairs of tasks, but when the present results are considered in the light of other recent experiments, there appears to be a relation between lateral bias on the free-vision face task and visual field differences in tachistoscopic identification. The pattern of results has implications for hypothesized individual differences among right-handers in cerebral dominance for verbal processes, input pathway dominance, and asymmetric arousal of the two cerebral hemispheres.     

Concurrent verbal interference of right and left proximal and distal upper extremity tapping

The purpose of this study was to investigate crossed and uncrossed control of the proximal (upper arm and shoulder) and distal (lower arm and hand) musculature of the arms using the dual-task paradigm. Forty-one strongly right-handed men performed a tapping task using primarily the musculature of the upper or lower arms, with and without concurrent verbal processing demands. The results showed that the left distal region was distinguished from the other three effector locations by its relative insensitivity to the demands of the dual-task (verbal processing) condition. Rapid alternating movements of the left arm were functionally independent from the left index finger location in response to dual-task demands. Dual verbal and tapping demands at this effector produced greater interference on both the primary and secondary task. The results preclude the attribution of interference effects to manual dominance factors alone. The results generally support anatomical accounts of increased ipsilateral control over left side arm but not hand movements. Neither the traditional cognitive hemispheric model nor the manual dominance hypothesis were adequate in accounting for the results. An alternative generalized capacity hypothesis was required to account for performance at the LE.     

Bilingual speech: Bilateral control?

Forty bilinguals from several language backgrounds were contrasted to a group of English-speaking monolinguals on a verbal-manual interference paradigm. For the monolinguals, concurrent finger-tapping rate during speech output tasks was disrupted only for the right hand, indicating left-hemisphere language dominance. Bilingual laterality patterns were a function of language used: native (L1) versus second acquired (L2), and age of L2 acquisition. Early bilinguals (L1 + L2 acquisition prior to age 6) revealed left-hemisphere dominance for both languages, whereas late bilinguals (L2 acquired beyond age 6) revealed left-hemisphere dominance only for L1 and symmetrical hemispheric involvement for L2.     

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.     

Vocal-manual trade-offs in hemispheric sharing of human performance control

Experiment 1 established the linear ordering of performance and rated difficulty of three finger-sequencing tasks. Experiment 2 embedded these tasks within a dual-task paradigm employing vocalization of words and nonwords as concurrent activities. Concurrent vocal activity interfered with right-more than with left handed performance, and this lateralized interference effect increased monotonically with increased sequence difficulty. Results are discussed in terms of hemispheric sharing of dual task performance control.     

Cerebral Organization of Motor Programming and Verbal Processing as a Function of Degree of Hand Preference and Familial Sinistrality

Seventy-six right- and left-handed subjects responded to monaurally presented verbal stimuli (CVs) using their right and left hands on separate occasions. Both degree of hand preference and familial sinistrality (FS) were taken into account. It was found that, contrary to expectation, the manual response interfered with the verbal perception task, but only in the consistent strong handers. The pattern of interference suggests that those with a consistent hand preference (right or left) have general motor programming in the left hemisphere. Those with an inconsistent strong hand preference probably have some degree of general motor programming in both hemispheres. No effect for FS was found for the lateralization of verbal processing or general motor programming.     

Asymmetry of Verbal-Manual Interference - Dissociation Between Rate and Variability in Left-Handers

In two experiments, 48 right-handed and 48 left-handed adults, respectively, performed speeded and consistent finger tapping with and without concurrent oral reading. Interference was measured in terms of change in tap-to-tap rate and variability. Experiment 1 confirmed a previous report that concurrent reading decreases the rate of speeded finger tapping and increases the rate of consistent tapping in right-handers, and that the right hand is affected more than the left. Experiment 2 showed that, for left-handers, concurrent reading decreases the rate of left-hand tapping more than right-hand tapping but increases the variability of the right hand more than the left. The double dissociation in left-handers between hand and dependent variable suggests that the speed and variability reflect different mechanisms of intertask interference. More generally, the findings illustrate the multidimensionality of motor performance and the risk of making inferences about neural organization on the basis of a single dependent measure.     

Hemispheric interference: A dual-task investigation of youngsters who stutter

Hemispheric interference was studied in this investigation by requiring 24 right-handed grade-school children who stutter to tap a button, as rapidly as possible, in five randomized conditions. Hand order was counterbalanced in the single-task silent control condition and in the four increasingly demanding dual-task conditions. In three of the experimental conditions tapping and speech occured concurrently. In the fourth dual-task condition the subjects were to vocalize the sound of a siren (in an irregularly patterned way) as they tapped the button. Analysis of the tapping rates in this two-by-five factorial study revealed statistically significant differences among hands and conditions. The tapping rate was faster with the right than with the left hand and the rate decreased as the demands of the dual-task conditions increased. Interaction was not evidenced; the interference pattern was similar in both hands across the conditions. Since interference was significantly present in both the speech and vocalic conditions, the data are not consistent with a laterality model. This finding and the increase in interference with increased attentional demand, however, are consistent with a capacity framework.     

Lateralized interference in finger tapping: comparisons of rate and variability measures under speed and consistency tapping instructions

Forty right-handed college subjects tapped with and without a verbal task under two instructional conditions (tap as quickly as possible vs. tap as consistently as possible) and two levels of verbal production (silent vs. aloud). The tapping task consisted of the alternate tapping of two keys with the index finger of the left vs. right hands, while the verbal task was anagram solution. Three rate and four variability measures of tapping performance were evaluated in the identification of lateralized interference. The results indicate that reliable lateralized interference, more right-hand than left-hand tapping disruption, was observed only for variability measures under instructions to tap as consistently as possible. Furthermore, only one of these variability measures was sensitive to an increase in lateralized interference produced by verbal production. Because of the limited demonstration of verbal laterality effects with the two-key tapping procedure in this study, conclusions suggest that the simpler manual task of repetitive tapping of one key should be viewed as the method of choice in future dual-task studies.     

Verbal asymmetries and levels of processing in an interactive dual-task paradigm

This study examined how the dual-task laterality paradigm produces patterns of cerebral asymmetry different from those obtained in studies of comparable single-laterality tasks. We systematically examined at what level of processing a concurrent verbal memory-load influences accuracy of recognition of laterally presented nouns relative to that in a control condition. Four groups of 20 subjects each were tested in an interactive dual-task paradigm requiring them to compare lateralized nouns directly with one of three nouns concurrently held in memory prior to accuracy of recognition. The groups differed according to the types of comparisons being made: physical identity, phonetic orthographic similarity, phonetic similarity using non-orthographic words, and category membership. Subjects in each group carried out three tasks. They were required to determine if a specified match had occurred between a memory-load word and the lateralized word, identify the lateralized word, and report the memory-load words. Another 20 subjects were assigned to a control laterality condition in which no concurrent memory-load was used. Control subjects were required to respond to a laterally presented word by pressing a reaction-time key to indicate recognition of the word and then to report the word. No significant visual-field differences occurred in accuracy of recognition for either the control or matching-task groups. However, reaction-time latencies and errors increased as a function of the level of processing. The accuracy of recognition did not support the predictions of Kinsbourne's attentional model but the reaction times provided some support for the concept of selective left-hemisphere interference proposed by Hellige. A limited-capacity approach was suggested as a possible alternative explanation of laterality effects.     

Concurrent task interference in stutterers: dissociating hemispheric specialization and activation

Using all four combinations of hand and foot, adult stutterers and nonstutterers performed a unimanual sequential finger tapping task together with a stimulus-contingent foot responding task. The two groups were similar in that both demonstrated more dual-task interference when using the ipsilateral than contralateral limb pairs. Contrary to a prediction based on a hypothesis that attributes stuttering to neural interference due to an ungated or unregulated activity flow between the hemispheres, stutterers did not show more interference than nonstutterers when using the contralateral limb pairs. The groups did differ, however, in terms of finger tapping interference associated with right- versus left-foot concurrent task responding. Nonstutterers showed more interference when using the left than right foot. This was interpreted in terms of the attentional demands that the foot responding task placed on a system with an inherent left-hemisphere attentional bias. The lack of a reliable difference in stutterers with respect to interference by the two feet is consistent with indications from other research that stutterers have a relatively labile system of hemispheric attention or activation. The results of the study are placed into the context of a general model of the brain mechanisms associated with stuttering.     

Lateralized finger-tapping interference produced by block design activities

Dual task procedures were used to examine hemispheric specialization for nonmanual block design activities. College subjects performed a finger-tapping task with each hand; on some trials concurrent WISC block design solutions were required. Patterns of lateralized interference in tapping under dual-task conditions indicated more left- than right-hemispheric involvement for males, while more bilateral involvement was shown for females.     

Patterns of hand preference for pairs of actions and the classification of handedness

Pairs of actions such as write × throw and throw × racquet were examined for items of the Annett hand preference questionnaire (AHPQ). Right (R) and left (L) responses were described for frequencies of RR, RL, LR, and LL pairings (write × throw etc.) in a large representative combined sample with the aim of discovering the distribution over the population as a whole. The frequencies of RL pairings varied significantly over the different item pairs but the frequencies of LR pairings were fairly constant. An important difference was found between primary actions (originally write, throw, racquet, match, toothbrush, hammer with the later addition of scissors for right‐handers) and non‐primary actions (needle and thread, broom, spade, dealing playing cards, and unscrewing the lid of a jar). For primary actions, there were similar numbers of right and left writers using the ‘other’ hand. For non‐primary actions more right‐handers used the left hand than for primary actions but more left‐handers did not use the right hand. That is, different frequencies of response to primary versus non‐primary actions were found for right‐handers but not for left‐handers. The pattern of findings was repeated for a corresponding analysis of left‐handed throwing × AHPQ actions. The findings have implications for the classification of hand preferences and for analyses of the nature of hand skill.     

Intrahemispheric response competition between vocal and unimanual performances in normam adult human males.

Subjects balanced a dowel rod vertically on the left and right index finger singly and while simultaneously repeating phrases. With right-handed subjects who had no left-handed relatives, concurrent verbalization shortened right- but not left-handed balancing. Increased phonetic difficulty of the phrases produced an increased decrement on right-handed balancing, but left-handed balancing was unchanged; it also produced more verbalization errors on trials with the right hand, but not with the left. Concurrent verbalization shortened balancing duration with both hands of left-handers. Right-handers with left-handed relatives produced variable results. Concurrent humming also selectively interfered with right-handed balancing. It was concluded that the results conform to an interpretation based on intrahemispheric interference between incompatible, simultaneously produced sets of responses.     

The handedness of Leonardo da Vinci: a tale of the complexities of lateralisation

The handedness of Leonardo da Vinci is controversial. Although there is little doubt that many of his well-attributed drawings were drawn with the left hand, the hatch marks of the shading going downwards from left to right, it is not clear that he was a natural left-hander, there being some suggestion that he may have become left-handed as the result of an injury to his right hand in early adulthood. Leonardo's lateralisation may be illuminated by an obscure passage in his notebooks in which he describes crouching down to look into a dark cave, putting his left hand on his knee, and shading his eyes with his right hand. We carried out a questionnaire survey, using 33 written and photographic items, to find whether this behaviour was typical of right handers or left handers. In fact the 'Leonardo task' showed almost no direct association with handedness, meaning that it contributes little to the immediate problem of elucidating Leonardo's handedness. However, the lateralisation of the task did relate to other aspects of behavioural laterality in surprisingly complex ways. This suggests that individual differences in handedness, and behavioural laterality in general, have a structural complexity which is not fully encompassed by simple measures of direction or degree of handedness.     

The creative thinking,environmental frustration,and self‐concept of left‐ and right‐handers

Abstract:

Left‐ (n = 12) and right‐handed (n = 12) college students were compared on creative thinking, environmental frustration, and self‐concept. It was hypothesized that because left‐handers regularly encounter equipment designed for right hand use, these individuals must use creative thinking to successfully interact with the environment. Results indicated that on the Environmental Frustration Questionnaire, left‐handers indicated significantly greater frustration with two of the six categories of objects, namely household tools (p < .005) and classroom desks (p < .005). On the Verbal and Figural Forms of the Torrance Tests of Creative Thinking, lefthanders scored significantly higher on the figural elaboration measure (p < .05). Finally, the hypothesis that handedness plays a larger role in the self‐concept of left‐handers than right‐handers was confirmed. Left‐handers were significantly more likely than right‐handers to mention their handedness when asked to describe themselves (p < .05).     

Visuospatial competency, handedness, and cerebral dominance

The present study addressed the question of Levy's (1974, Psychobiological implications of bilateral assymetry. In S. Dimond &; J. G. Beaumont, Hemispheric function in the human brain, NY: Halstead. Pp. 121–183.) proposal that left handers would have lowered spatial skills relative to verbal skills. In the first part of the study, performance on the PMA (visuospatial subtest) and WAIS Block Design subtest were compared between right and left handed high school and college samples. No support could be found for deficient visuo-spatial performance in the left handers. In the second part of the experiment, no relative impairment of visuospatial skills was found when subjects were classified into predicted speech dominance groups on the basis of a dichotic listening task and/or a visual half-field task. An extreme groups comparison of the most left dominant and most right dominant groups again yielded no significant differences in visuo-spatial performance. Finally, the relationship between degree of speech lateralization and visuo-spatial skills was examined. Only partial support for differences in cerebral organization for speech in left handers was found in the college sample.     

A dual-task investigation of young stutterers and nonstutterers

Twenty right-handed grade-school stutterers and nonstutterers matched for sex, handedness, and age were the subjects of this neuromotor investigation. They were required to tap a button as rapidly as possible in a single-task control condition, in three increasingly demanding dual-task conditions in which finger-tapping and speech occured concurrently, and in a dual-task condition in which the subjects finger-tapped and vocalized the sound of a siren. The conditions were randomized, and hand order was counterbalanced. The overall tapping rate of the nonstutterers was statistically faster than that of the stutterers for both the right and left hand. Relative to the single-task silent control condition, the tapping rates of both groups decreased as the dual-task speech conditions became more demanding. However, the tapping rate of the nonstutterers was significantly faster across the speech conditions. Neither the group by hand, group by condition, or group by hand by condition interaction was statistically significant. The stutterers responded like the nonstutterers, though more slowly, providing support for the current contentions that the neuromotor system of stutterers is less robust than that of nonstutterers and more affected by the demands of speech production.     

习得性空间联结的迁移依赖于语义工作记忆

采用练习迁移范式与双任务范式相结合的设计来探讨练习所习得的空间联结在工作记忆中如何表征。被试先进行不一致空间的刺激—反应映射练习任务, 五分钟后, 随机迁移到单任务(Simon任务)或者双任务(Simon任务+语义工作记忆负荷任务或空间工作记忆负荷任务)。结果发现：不一致的练习能使单任务出现反转的Simon效应, 但语义工作记忆负荷会使反转的Simon效应消失, 而空间工作记忆负荷却对反转的Simon效应没有影响。实验结果表明练习产生的空间联结依赖于语义工作记忆。