Left-Handers and Right-Handers Compared on a Motor Task

Handwriting kinematics during learning to write with the dominant left hand in converted left-handers

Converting left-handers to their non-dominant right hand was previously widespread, particularly for handwriting. The present study aimed to explore the extent to which adult, converted left-handers can learn writing with their dominant left hand during a 2-year training program. Eleven converted left-handers participated in the training. Handwriting kinematics were assessed at regular intervals (seven sessions) and compared to those of 11 innate left-handed controls matched for age, gender, and overall handedness score for basic (Finger, Wrist, Circle) and complex (Sentence, Copy) handwriting tasks. Regarding basic tasks in the training group, we found rapid increases in left and right-hand frequency and no significant differences between both hands at any time point, indicating successful hand transfer. After 24 months, training participants significantly surpassed controls for writing frequency in basic tasks with their left hand. For complex tasks, we identified significant increases in the training groups' left-hand writing frequency and duration between the first and last session. While training participants' left-hand writing remained significantly slower than their right-hand writing, statistics confirmed final differences between hands only for the duration of the Sentence task. Importantly, left-hand writing in the training group was characterized by lower frequency, lower automaticity, and prolonged duration after 24 months compared to innate left-handers. With training participants' left-hand writing skills significantly increasing for complex tasks and no final statistically significant differences between hands for frequency and automaticity, the program was considered effective. Nevertheless, within 2 years, training participants did not reach innate left-handers handwriting proficiency for complex tasks. Underlying reasons may be various, such as a non-optimal training program, a sensitive period for learning to write, irreversible neural changes during conversion in childhood, age-related decline of motor learning capacity, or retrograde interference between right- and left-hand writing.

Age and Not the Preferred Limb Influences the Kinematic Structure of Pointing Movements

In goal-directed movements, effective open-loop control reduces the need for feedback-based corrective submovements. The purpose of this study was to determine the influence of hand preference and aging on submovements during single- and two-joint pointing movements. A total of 12 young and 12 older right-handed participants performed pointing movements that involved either elbow extension or a combination of elbow extension and horizontal shoulder flexion with their right and left arms to a target. Kinematics were used to separate the movements into their primary and secondary submovements. The older adults exhibited slower movements, used secondary submovements more often, and produced relatively shorter primary submovements. However, there were no interlimb differences for either age group or for the single- and two-joint movements. These findings indicate that open-loop control is similar between arms but compromised in older compared to younger adults.

Exploring the Interaction Between Handedness and Body Parts Ownership by Means of the Implicit Association Test

The experience of owning a body is built upon the integration of exteroceptive, interoceptive, and proprioceptive signals. Recently, it has been suggested that motor signals could be particularly important in producing the feeling of body part ownership. One thus may hypothesize that the strength of this feeling may not be spatially uniform; rather, it could vary as a function of the degree by which different body parts are involved in motor behavior. Given that our dominant hand plays a leading role in our motor behavior, we hypothesized that it could be more strongly associated with one’s self compared to its non-dominant counterpart. To explore whether this possible asymmetry manifests as a stronger implicit association of the right hand (vs left hand) with the self, we administered the Implicit Association Test to a group of 70 healthy individuals. To control whether this asymmetric association is human-body specific, we further tested whether a similar asymmetry characterizes the association between a right (vs left) animal body part with the concept of self, in an independent sample of subjects (N = 70, 140 subjects total). Our results revealed a linear relationship between the magnitude of the implicit association between the right hand with the self and the subject’s handedness. In detail, the strength of this association increased as a function of hand preference. Critically, the handedness score did not predict the association of the right-animal body part with the self. These findings suggest that, in healthy individuals, the dominant and non-dominant hands are differently perceived at an implicit level as belonging to the self. We argue that such asymmetry may stem from the different roles that the two hands play in our adaptive motor behavior.

Hand preference for the visual and auditory modalities in humans

The sensory dominance effect refers to the phenomenon that one sensory modality more frequently receives preferential processing (and eventually dominates consciousness and behavior) over and above other modalities. On the other hand, hand dominance is an innate aspect of the human motor system. To investigate how the sensory dominance effect interacts with hand dominance, we applied the adapted Colavita paradigm and recruited a large cohort of healthy right-handed participants (n = 119). While the visual dominance effect in bimodal trials was observed for the whole group (n = 119), about half of the right-handers (48%) showed a visual preference, i.e., their dominant hand effect manifested in responding to the visual stimuli. By contrast, 39% of the right-handers exhibited an auditory preference, i.e., the dominant hand effect occurred for the auditory responses. The remaining participants (13%) did not show any dominant hand preference for either visual or auditory responses. For the first time, the current behavioral data revealed that human beings possess a characteristic and persistent preferential link between different sensory modalities and the dominant vs. non-dominant hand. Whenever this preferential link between the sensory and the motor system was adopted, one dominance effect peaks upon the other dominance effect's best performance.

The effects of background music on neural responses during reading comprehension

The effects of background speech or noise on visually based cognitive tasks has been widely investigated; however, little is known about how the brain works during such cognitive tasks when music, having a powerful function of evoking emotions, is used as the background sound. The present study used event-related potentials to examine the effects of background music on neural responses during reading comprehension and their modulation by musical arousal. Thirty-nine postgraduates judged the correctness of sentences about world knowledge without or with background music (high-arousal music and low-arousal music). The participants’ arousal levels were reported during the experiment. The results showed that the N400 effect, elicited by world knowledge violations versus correct controls, was significantly smaller for silence than those for high- and low-arousal music backgrounds, with no significant difference between the two musical backgrounds. This outcome might have occurred because the arousal levels of the participants were not affected by the high- and low-arousal music throughout the experiment. These findings suggest that background music affects neural responses during reading comprehension by increasing the difficulty of semantic integration, and thus extend the irrelevant sound effect to suggest that the neural processing of visually based cognitive tasks can also be affected by music.

Quantitative assessment of fine motor skills in children using magnetic sensors

AIM

We aimed to establish objective and quantitative data on fine motor development in typically developing children using magnetic sensors.

METHODS

The study included 110 Japanese elementary school children volunteers (57 boys, 53 girls). The participants were instructed to tap their thumbs and index fingers together repetitively for 10 s. After attaching coils to the participants' right and left thumbs and index fingers, participants executed "in-phase" and "anti-phase" tapping. We used two-way analysis of variance to analyze the influences of age and sex on fine motor development.

RESULTS

The "number of taps" significantly increased with age, while the "standard deviation (SD) of tapping interval" significantly decreased. More than half of the "acceleration" parameters significantly increased with age. Boys performed significantly faster than girls in some parameters of "velocity" and "acceleration," while girls had significantly lower "SD of local maximum velocity in opening motion" and "SD of local minimum velocity in closing motion."

DISCUSSION

We established both objective and quantitative reference data on fine motor development in typically developing Japanese children aged between 7 and 12 years using magnetic sensors. We revealed that this system can monitor real-time details of the parameters involved in the finger-tapping movement in children without complications. This device could be useful for obtaining objective and quantitative data on fine motor skills in the clinical assessment of developmental coordination disorder, assessments of educational intervention, or rehabilitation and discovery of new therapeutic agents.

The dominant limb preferentially stabilizes posture in a bimanual task with physical coupling

Humans are endowed with an ability to skillfully handle objects, like when holding a jar with the nondominant hand while opening the lid with the dominant hand. Dynamic dominance, a prevailing theory in handedness research, proposes that the nondominant hand is specialized for postural stability, which would explain why right-handed people hold the jar steady using the left hand. However, the underlying specialization of the nondominant hand has only been tested unimanually, or in a bimanual task where the two hands had different functions. Using a dedicated dual-wrist robotic interface, we tested the dynamic dominance hypothesis in a bimanual task where both hands carry out the same function. We examined how left- and right-handed subjects held onto a vibrating virtual object using their wrists, which were physically coupled by the object. Muscular activity of the wrist flexors and extensors revealed a preference for cocontracting the dominant hand during both holding and transport of the object, which suggests proficiency in the dominant hand for stabilization, contradicting the dynamic dominance hypothesis. While the reliance on the dominant hand was partially explained by its greater strength, the Edinburgh inventory was a better predictor of the difference in the cocontraction between the dominant and nondominant hands. When provided with redundancy to stabilize the task, the dominant hand preferentially cocontracts to absorb perturbing forces.NEW & NOTEWORTHY We found that subjects prefer to stabilize a bimanually held object by cocontracting their dominant limb, contradicting the established view that the nondominant limb is specialized toward stabilization.

High-density EEG mobile brain/body imaging data recorded during a challenging auditory gait pacing task

In this report we present a mobile brain/body imaging (MoBI) dataset that allows study of source-resolved cortical dynamics supporting coordinated gait movements in a rhythmic auditory cueing paradigm. Use of an auditory pacing stimulus stream has been recommended to identify deficits and treat gait impairments in neurologic populations. Here, the rhythmic cueing paradigm required healthy young participants to walk on a treadmill (constant speed) while attempting to maintain step synchrony with an auditory pacing stream and to adapt their step length and rate to unanticipated shifts in tempo of the pacing stimuli (e.g., sudden shifts to a faster or slower tempo). High-density electroencephalography (EEG, 108 channels), surface electromyography (EMG, bilateral tibialis anterior), pressure sensors on the heel (to register timing of heel strikes), and goniometers (knee, hip, and ankle joint angles) were concurrently recorded in 20 participants. The data is provided in the Brain Imaging Data Structure (BIDS) format to promote data sharing and reuse, and allow the inclusion of the data into fully automated data analysis workflows.

Constraints in the Performance of Bimanual Tasks and Their Expression in Unskilled and Skilled Subjects

Unskilled and skilled subjects were asked to perform a variety of bimanual tapping tasks. Three major effects were seen. First, right-handers performed dual tasks better when the preferred hand took the “figure” and when the nonpreferred hand took the “ground” of the dual movement. This effect was not seen in left-handers. Second, subjects performed a simple slow/fast dual task better when they commenced the task with the fast rather than with the slow hand. This effect was seen in right- and lefthanders. Third, both unskilled and skilled subjects showed marked interdependence of movements such that performance of one hand was a function of movements in the other hand. The results are in agreement with a model that postulates the presence of a superordinate control mechanism that initiates action in subordinate control mechanisms, which in turn set the movement trajectories in the two hands. The results also show that attention is an important factor in the interaction between these two levels of control.

Bimanual tapping of a syncopated rhythm reveals hemispheric preferences for relative movement frequencies

In bimanual multifrequency tapping, right-handers commonly use the right hand to tap the relatively higher rate and the left hand to tap the relatively lower rate. This could be due to hemispheric specializations for the processing of relative frequencies. An extension of the double-filtering-by-frequency theory to motor control proposes a left hemispheric specialization for the control of relatively high and a right hemispheric specialization for the control of relatively low tapping rates. We investigated timing variability and rhythmic accentuation in right handers tapping mono- and multifrequent bimanual rhythms to test the predictions of the double-filtering-by-frequency theory. Yet, hemispheric specializations for the processing of relative tapping rates could be masked by a left hemispheric dominance for the control of known sequences. Tapping was thus either performed in an overlearned quadruple meter (tap of the slow rhythm on the first auditory beat) or in a syncopated quadruple meter (tap of the slow rhythm on the fourth auditory beat). Independent of syncopation, the right hand outperformed the left hand in timing accuracy for fast tapping. A left hand timing benefit for slow tapping rates as predicted by the double-filtering-by-frequency theory was only found in the syncopated tapping group. This suggests a right hemisphere preference for the control of slow tapping rates when rhythms are not overlearned. Error rates indicate that overlearned rhythms represent hierarchically structured meters that are controlled by a single timer that could potentially reside in the left hemisphere.

Human Handedness: The Influence of Learning

55 subjects were divided by writing-hand preference and further divided into control and experimental conditions. All subjects were administered a manipulative skill at pretest, counterbalanced for starting hand. Experimental subjects were given 5 practice sessions, and then all subjects were administered a posttest. Posttest scores of both hands of experimental subjects indicated significant improvement as a result of practice, with the nonpreferred hand showing no significant difference from the preferred hand. These findings were related to the etiology of handedness which is hypothesized to involve two factors, one verbal and dichotomous, the other nonverbal and continuous.

On the Relation between Footedness and Handedness

The relation between handedness and footedness was examined for 32 righthanders and 32 lefthanders. On a speed-tapping task, righthanders showed a significant right-hand and right-foot advantage. Lefthanders showed a significant left-hand advantage and a significant right-foot advantage. This appears to support previous work. However, while the right-foot advantage of righthanders proves robust over different replications, the right-foot advantage of lefthanders does not show such robustness. Results show tacit agreement with Annett's 1972 model which suggests an inherent right-shift bias for righthanders and no inherent directional bias for lefthanders.

Starting off on the right foot: strong right-footers respond faster with the right foot to positive words and with the left foot to negative words

Recent studies have provided evidence for an association between valence and left/right modulated by handedness, which is predicted by the body-specificity hypothesis (Casasanto, 2009) and also reflected in response times. We investigated whether such a response facilitation can also be observed with foot responses. Right-footed participants classified positive and negative words according to their valence by pressing a key with their left or right foot. A significant interaction between valence and foot only emerged in the by-items analysis. However, when dividing participants into two groups depending on the strength of their footedness, an interaction between valence and left/right was observed for strong right-footers, who responded faster with the right foot to positive words, and with the left foot to negative words. No interaction emerged for weak right-footers. The results strongly support the assumption that fluency lies at the core of the association between valence and left/right.

Computerized measures of finger tapping: effects of hand dominance, age, and sex

Computerized measures of digit tapping rate were obtained over 3 successive, 10-sec. periods in the right and left index fingers, from a community sample of 1,519 participants (ages 18 to 65 years; 607 men, 912 women). Differences between the dominant and non-dominant hands were found for tapping rate, movement initiation, and button down times, and the decline in tapping rate over the successive, 10-sec. periods. Declines were found in tapping rate in older participants in association with increased intertap variability. Men had higher tapping rates than women in all age ranges. The computerized finger tapping test is an efficient and precise measure of tapping speed and kinetics of potential utility in research and clinical studies of motor performance.

Hand usage pattern and upper body discomfort of desktop touchscreen users

A laboratory study was conducted to determine how users of different handedness interact with desktop touchscreen displays and how the hand usage pattern influences their body discomfort development. Twenty-one participants in three different handedness groups conducted simple web-browsing for 30 minutes using a 23″ touchscreen display while their subjective body discomfort, frequency of use of each hand and touch area preference were periodically quantified. Participants reported a gradual increase in body discomfort during web-browsing, and the increments in body discomfort varied between handedness groups for some body parts. Results also show that right-handed participants had stronger laterality than the left-handed, and ambidextrous participants used both hands more evenly than other participants, suggesting associations between the hand usage pattern and body discomfort development. Findings of the current study suggest that body discomfort of desktop touchscreen display users could be moderated by user-interface improvements and user training.

PRACTITIONER SUMMARY

Body discomfort development of desktop touchscreen users may be influenced by their hand usage pattern. Findings of this laboratory study suggest that user discomfort may be moderated by placing menu items in the lower area within the display or training users to alternate hands when conducting touch gestures.

Hand preference, performance abilities, and hand selection in children

It is widely know that the pattern of human handedness is such that approximately 90% of the population is right handed with the remainder being left handed, at least in the adult population. What is less well understood is how handedness develops and at what age adult-like handedness patterns emerge. Quantified in terms of both preference and performance, a plethora of different behavioral assessments are currently in use with both children and adults. Handedness questionnaires are commonly used; however, these possess inherent limitations, considering their subjective nature. Hand performance measures have also been implemented; however, such tasks appear to measure different components of handedness. In addition to these traditional measures, handedness has been successfully assessed through observation of hand selection in reaching, which has proven to be a unique and effective manner in understanding the development of handedness in children. Research over the past several decades has demonstrated that young children display weak, inconsistent hand preference tendencies and are slower with both hands. Performance differences between the hands are larger for young children, and consistency improves with age. However, there remains some controversy surrounding the age at which hand preference and hand performance abilities can be considered fully developed. The following paper will provide a review of the literature pertaining to hand preference, performance abilities and hand selection in children in an attempt to ascertain the age at which adult-like patterns of hand preference and performance emerge.

Relative performance of the two hands in simple and choice reaction time tasks

There is evidence that the left hemisphere is more competent for motor control than the right hemisphere. This study investigated whether this hemispheric asymmetry is expressed in the latency/duration of sequential responses performed by the left and/or right hands. Thirty-two right-handed young adults (16 males, 16 females; 18-25 years old) were tested in a simple or choice reaction time task. They responded to a left and/or right visual target by moving their left and/or right middle fingers between two keys on each side of the midline. Right hand reaction time did not differ from left hand reaction time. Submovement times were longer for the right hand than the left hand when the response was bilateral. Pause times were shorter for the right hand than the left hand, both when the responses were unilateral or bilateral. Reaction time results indicate that the putatively more efficient response preparation by the left hemisphere motor mechanisms is not expressed behaviorally. Submovement time and pause time results indicate that the putatively more efficient response execution by the left hemisphere motor mechanisms is expressed behaviorally. In the case of the submovements, the less efficient motor control of the left hand would be compensated by a more intense attention to this hand.

Associations between handedness and cerebral lateralisation for language: a comparison of three measures in children

It has been known for many years that hand preference is associated with cerebral lateralisation for language, but the relationship is weak and indirect. It has been suggested that quantitative measures of differential hand skill or reaching preference may provide more valid measures than traditional inventories, but to date these have not been validated against direct measures of cerebral lateralisation. We investigated the associations of three different handedness assessments; 1) a hand preference inventory, 2) a measure of relative hand skill, and 3) performance on a reaching task; with cerebral lateralisation for language function as derived from functional transcranial Doppler ultrasound during a language production task, in a group of 57 typically developing children aged from 6 to 16 years. Significant correlations between cerebral lateralisation for language production and handedness were found for a short version of the inventory and for performance on the reaching task. However, confidence intervals for the correlations overlapped and no one measure emerged as clearly superior to the others. The best handedness measures accounted for only 8–16% of the variance in cerebral lateralisation. These findings indicate that researchers should not rely on handedness as an indicator of cerebral lateralisation for language. They also imply that lateralisation of language and motor functions in the human brain show considerable independence from one another.

Sulcal morphology and volume of Broca's area linked to handedness and sex

We investigated the effect of handedness and sex on: (i) sulcal contours defining PO and PTR and (ii) volume estimates of PO and PTR subfields in 40 left- and 42 right-handers. Results show an effect of handedness on discontinuity of the inferior frontal sulcus (IFS: P<0.01). Discontinuity of IFS was observed in: 43% left- and 62% right hemispheres in right-handers and in 65% left- and 48% right-hemispheres in left-handers. PO volume asymmetry was rightward in left-handed males (P=0.007) and females (P=0.02), showed a leftward trend in right-handed males (P=0.06), and was non-asymmetrical in right-handed females (P=0.96, i.e. left- and right-hemisphere PO volumes did not differ significantly). PO volume asymmetry in males differed significantly between handedness groups (P=0.001). Findings indicate a high degree of variability in the sulcal contours of PO and PTR and volume asymmetry of PO: the factors sex and handedness can explain some of this variability.

More than just tapping: index finger-tapping measures procedural learning in schizophrenia

BACKGROUND

Finger-tapping has been widely studied using behavioral and neuroimaging paradigms. Evidence supports the use of finger-tapping as an endophenotype in schizophrenia, but its relationship with motor procedural learning remains unexplored. To our knowledge, this study presents the first use of index finger-tapping to study procedural learning in individuals with schizophrenia or schizoaffective disorder (SCZ/SZA) as compared to healthy controls.

METHODS

A computerized index finger-tapping test was administered to 1169 SCZ/SZA patients (62% male, 88% right-handed), and 689 healthy controls (40% male, 93% right-handed). Number of taps per trial and learning slopes across trials for the dominant and non-dominant hands were examined for motor speed and procedural learning, respectively.

RESULTS

Both healthy controls and SCZ/SZA patients demonstrated procedural learning for their dominant hand but not for their non-dominant hand. In addition, patients showed a greater capacity for procedural learning even though they demonstrated more variability in procedural learning compared to healthy controls. Left-handers of both groups performed better than right-handers and had less variability in mean number of taps between non-dominant and dominant hands. Males also had less variability in mean tap count between dominant and non-dominant hands than females. As expected, patients had a lower mean number of taps than healthy controls, males outperformed females and dominant-hand trials had more mean taps than non-dominant hand trials in both groups.

CONCLUSIONS

The index finger-tapping test can measure both motor speed and procedural learning, and motor procedural learning may be intact in SCZ/SZA patients.

An investigation into manual asymmetries in grasp behavior and kinematics during an object manipulation task

Manual asymmetries in the control of movements have been investigated in a variety of experimental paradigms. Initial studies demonstrated that the dominant right hand has advantages over the non-dominant left hand in many aspects of motor control. However, more recent studies have shown that the presence and extent of these asymmetries depends on the task context and accuracy demands. Typically, manual asymmetries on a motor planning and motor execution level are examined separately. However, given that recent research has demonstrated that specific task constraints do not influence both levels equally, the purpose of the present experiment was to investigate manual asymmetries in motor planning and execution. To this end, initial grasp behavior (motor planning) and kinematics (motor execution) were examined in thirteen right-handed participants during a unimanual grasping and placing task. We specifically manipulated grasping hand, target location, object end orientation, and object grasp time at the start location. There were three main findings. First, motor planning or movement execution was similar regardless of grasping hand. Second, prospectively planned actions were influenced by target location and the required end orientation of the object. Third, the amount of time spent in an initial posture did not influence initial grasp postures. However, it did alter the movement kinematics during the grasping (approach phase) and placing (transport phase) portion of the task. We posit that grasping and placing movements are comprised of an initial grasp and a transport component, which are differentially influenced by task constraints.

Description and Validation of a Flexible and Broadly Usable Handedness Questionnaire

Empirical evidence is provided which shows that handedness questionnaires should: (a) comprise items that cover skilled and unskilled activities; (b) be sufficiently long to capture a ''mass effect'' of variability in lateral preferences over a range of items; and (c) allow graded answer options for individual items rather than forced left/right choices. When using questionnaires that meet these criteria, it is possible to establish significant correlations between hand preference and performance even within a group of right-handers. In addition, such questionnaires are flexible enough to accommodate a great variety of handedness classification schemes.

Characteristics of the bimanual deficit using grip strength

Grip strength was used to evaluate bimanual functioning and the bimanual deficit as a measure of the relationship between the hands and the hemispheres. Participants were 174 right-handed individuals. Experiment 1 measured maximal, unimanual, and bimanual grips. There were two bimanual, simultaneous grip conditions: (1) symmetrical (hands perform the same grip) and (2) asymmetrical (different grips for each hand). Decrements were equivalent for preferred and nonpreferred hands and were similar for males and females. Experiment 2 consisted of three variations of the bimanual, asymmetrical grip condition used in Experiment 1. Emphasis was imposed on a single hand via a performance criterion and feedback. Results indicated that emphasis imposed on either hand produced a strength increment compared to that hand's baseline, but did not affect the concurrently performing hand. Results suggest that the bimanual coordination is governed at a non-lateralised or inter-hemispheric level for both males and females.

Effect of stick use on rapid unimanual tapping in drummers

Drummers achieve impressive musical performance by using drumsticks. The present study investigated the effect of drumstick use on rapid unimanual tapping performance. 17 drummers tapped a force transducer as fast as possible for 10 sec. with a finger and a drumstick. No significant difference between finger and stick tapping was found for tapping speed and variability of peak force, but there were significant differences in contact time with the tapping surface, mean peak force, and intertap interval variability: Stick tapping had a shorter contact time, a larger peak force, and more stable intertap interval than did finger tapping. Thus, stick use makes it possible to produce a larger impact force and enhances the ability to control timing during rapid manual movement, allowing drummers to play drums powerfully and stably, which is clearly important for the role they have in controlling or enhancing musical rhythm.

Hand preference for precision grasping predicts language lateralization

We investigated whether or not there is a relationship between hand preference for grasping and hemispheric dominance for language--and how each of these is related to other traditional measures of handedness. To do this we asked right- and left-handed participants to put together two different sets of 3D puzzles made out of big or very small LEGO pieces. Participants were also given two self-reported handedness questionnaires, as well as tests of grip force and finger tapping speed. A language lateralization (dichotic listening) test was also administered. We found a positive correlation between hand use for precision grasping and language lateralization (i.e. the more participants used their right hand for grasping the small LEGO pieces, the more language was lateralized to the left hemisphere). In addition, we identified two populations of left-handers according to their grasping performance: 'left-right-handers', who behaved exactly like right-handers; and 'left-left-handers' whose performance was the mirror image of that of right-handers. Finally, we found an increase in right-hand use when right-handers and 'left-right-handers' had to pick up the small LEGO pieces. We discuss our results in relation to recent notions of left-hemisphere specialization for visually guided actions and its relationship with the evolution of language.

Manual asymmetry in a complex coincidence-anticipation task: handedness and gender effects

This study investigated the effects of handedness and gender on manual asymmetry in the performance of a complex coincidence-anticipation task. Left-handed (N=63) and right-handed (N=93) undergraduate students (78 males, 78 females) were required to press six buttons sequentially in conjunction with visual stimulation provided by a coincidence-anticipation apparatus. Participants were further separated into subgroups based on the degree of hand preference. Timing accuracy (AE, CE, VE) and timing response (IT, MT, AT) were analysed. Results showed that, concerning accuracy, (i) strong left-handers were more accurate than the other groups; (ii) performance with the preferred hand was superior to that of the non-preferred hand; and (iii) males outperformed females. Concerning timing response, (i) the preferred hand was faster than the non-preferred hand for movement time and (ii) males were faster in initiating the movement than females. These findings indicate that coincidence-anticipation competence appears to be influenced by hand preference, performing hand, and gender. In addition, findings are discussed in the framework of the hemispheric functional lateralisation for the planning and organisation of movement execution.

Investigating the stabilising and mobilising features of footedness

This study investigated lower limb laterality for stabilising and mobilising actions in 10 right- and 10 mixed-footed participants by determining, via the Waterloo Footedness Questionnaire--Revised (WFQ-R), the preferred foot in carrying out a range of stabilising and mobilising activities and by recording foot performance on standing balance and ball juggling. The log odds ratio (lambda score) was used to quantify the degree of laterality in task performance. Differences between the stability and mobility scores and the two groups were analyzed using a 2 (Group) x 2 (Task) ANOVA model with repeated measures on Task. Right- and mixed-footed participants differed significantly in the stability but not in the mobility items of the WFQ-R. No significant between-group differences were noted in either ball-juggling or standing balance performance. Mixed-footed participants had a significant right-left foot difference in standing balance, whereas both groups had a significant right-left foot difference in ball juggling. It is concluded that preference is not a steady attribute across the mobility and stability items of the WFQ-R and appears to be dependent on the behavioural context of a particular task. Results further indicated a lack of concordance between questionnaire and performance-based measures suggesting that these two methods of measuring laterality may be indicators of different underlying factors.

Upper Limb Asymmetries in the Matching of Proprioceptive Versus Visual Targets

The purpose of the current study was to determine the extent to which “sensory dominance” exists in right-handers with respect to the utilization of proprioceptive versus visual feedback. Thirteen right-handed adults performed two target-matching tasks using instrumented manipulanda. In the proprioceptive matching task, the left or right elbow of blindfolded subjects was passively extended by a torque motor system to a target position and held for 3 s before being returned to the start position. The target angle was then matched with either the ipsilateral or contralateral arm. In the second task, visual matching, circular targets were briefly projected to either side of a visual fixation point located in front of the subject. Subjects then matched the target positions with a laser pointer by moving either the ipsilateral or contralateral arm. Overall, marked arm differences in accuracy were seen based on the type of sensory feedback used for target presentation. For the proprioceptive matching task errors were smaller for the nonpreferred left arm, whereas during the visual matching task smaller errors were found for the preferred right arm. These results suggest a left arm/right hemisphere advantage for proprioceptive feedback processing and a right arm/left hemisphere advantage for visual information processing. Such asymmetries may reflect fundamental differences between the two arm/hemisphere systems during the performance of bimanual tasks where the preferred arm requires visual guidance to manipulate an object, whereas the nonpreferred stabilizes that object on the basis of proprioceptive feedback.

How Good People are at Estimating their Own Performance? A Study of the Relationship between Hand Preference and Motor Performance

This article examines the relationship between the awareness of hand preference and hand and foot performance among right-, left- and mixed-handers (n = 224). The hand preference was assessed using a handedness inventory. Hand and foot performances were measured using rapid index finger or toe tapping. A significant interaction between hand preference and the tapping rate indicated that in left-handers, left tapping was faster than right tapping and in right-handers, right tapping was faster than left tapping regardless of effector, finger or toe. The mixed-handers, however, did not show differences between left and right tapping performance. Correlations between performances were highest between hands or between feet. Also, hand performance was more strongly positively associated to foot performance in the mixed- and left-handers than right-handers. Similar inter-limb performance in mixed-handers tends to implicate inconsistent or undeveloped cerebral lateralisation. The results indicate that self-awareness of the pattern of hand use significantly relates to hand and foot performance.

Task demands affect manual asymmetries in pegboard performance

Previous work by Bryden and Roy (1999) showed a larger performance difference between the hands for placing pegs into holes on the Grooved Pegboard test than for removing pegs from the holes. The authors argued that these data provided evidence of the importance of task demands in manual asymmetries. However the study failed to control for the differing starting positions of the pegs. To clarify this possible confound, the purpose of the current investigation was to determine the influence of starting position on the between-hand performance differences on the Grooved Pegboard Test. To do so, both the start and end positions were manipulated, such that participants moved the pegs from the receptacle to another receptacle or to a set of holes, or participants moved the pegs from a set of holes to a receptacle or another set of holes. A total of 30 right-handed individuals (as classified using the Waterloo Handedness Questionnaire) participated in the experiment, completing five trials with each hand for each of the four conditions. While no significant effects of start position were found, a significant interaction between hand and end position, F(1.29) = 30.85, P<.001, was found for the time to complete the task, where larger differences between the hands, fovouring the right hand, were seen for placing pegs into the holes as opposed to the receptacles. This effect was also found when the data were expressed using a laterality quotient. The results are discussed in terms of the influence of task complexity on manual asymmetries.

Cultural and environmental influences on footedness: cross-sectional study in urban and semi-urban Malawi

The present study was designed to assess cultural and environmental pressure against left-foot preference in urban and semi-urban Malawi. The findings demonstrated that, when compared to handedness, footedness appeared to be less biased behavioral laterality in culturally restrictive communities. The percentage of responders with negative views on left-foot preference was lower than that on left-hand preference (57% vs. 75%) and a smaller proportion of volunteers suggested that left-footers should be forced to change the foot (63.5% vs. 87.6%). In total, mobilizing and stabilizing tasks scored similar proportions of negative responses. Expectation of inferior performance of the left foot than the right one was the major reason for negative views on left-foot preference. Gender and driving experience had significant but weak effect on the view on left-foot preference. Most of the responders (74%) suggested that left-footers should change the foot in early family environment.

Task-dependent asymmetries in the utilization of proprioceptive feedback for goal-directed movement

Whereas the majority of studies regarding upper limb asymmetries in motor performance have focused on preferred arm dominance for producing motor output, studies exploring the role of sensory feedback have suggested that the preferred and non-preferred arms are specialized for different aspects of movement. A recent study by Goble et al. (2006) found evidence of a non-preferred left arm (and presumably right hemisphere) proprioceptive dominance for a target matching task that required subjects to both memorize and transfer across hemispheres proprioceptive target information. This paradigm contrasted previous studies of proprioceptive matching asymmetry that explored only memory-based matching and produced equivocal results. The purpose of the present study, therefore, was to examine task-dependent asymmetries in proprioceptive matching performance, including differences related to active versus passive presentation of the matching target. It was found that the non-preferred left arm of right handers matched target elbow angles more accurately than the preferred arm, but only in the matching condition that required both memory and interhemispheric transfer. Task-dependent asymmetries were not affected by the mode of target presentation and assessment of matching kinematics revealed differences in strategy for both the speed and smoothness of targeted movements. Taken together, these results suggest that the non-preferred arm/hemisphere system is specialized for the processing of movement-related proprioceptive feedback.

Control of the dominant and nondominant hand: exploitation and taming of nonmuscular forces

Movements of the dominant and nondominant hand have been claimed to differ with respect to how they take intersegmental dynamics into account. Consistent with this claim, movements of the dominant hand are hypothesized to better exploit the intrinsic limb dynamics, whereas movements of the nondominant hand are controlled to make the intrinsic dynamics ineffective as far as this is possible. For rapid finger oscillations this hypothesis implies a higher level of co-contractions in the nondominant than in the dominant hand. Replicating previous findings on finger tapping, finger oscillations of the dominant hand were faster and less variable than those of the nondominant hand. More importantly, the variance of the relative difference between myoelectric signals of antagonistic muscles and thus the power of reciprocal myoelectric activity was smaller in the nondominant hand, indicating a relatively higher level of co-contractions than in the dominant hand. In addition, a spectral decomposition of the total power of the relative-difference signal revealed stronger relative power in the frequency band of the finger oscillations in the dominant than in the nondominant hand. These findings are consistent with the hypothesis that for the dominant hand more accurate feedforward control is possible based on a more accurate internal model of limb dynamics.

Cultural and environmental pressure against left-hand preference in urban and semi-urban Malawi

The study assessed views of teachers, pupils and their guardians on left-hand preference. Seventy-five percent of the responders indicated that the left hand should not be preferred for habitual activities and 87.6% of them indicated that left-handers should be forced to change the hand. Gender had significant effect on the view on left hand preference (df = 1, OR (odds ratio) = 0.465, p = 0.027). Giving a handshake when greeting a person, drawing and writing were the three top target activities against left-hand preference. An assumption that the left hand is less skilled and less powerful than the right one was the most common reason for negative view on left-hand use. Most of volunteers reported that parents and close relatives were the primary group of people who usually discourage left-hand use. Eighty point one percent of the responders indicated that people should stop preferring the left hand as soon as somebody noticed their left-handedness. The results indicated that cultural and environmental pressures might significantly affect visibility of left-handedness in urban Malawian populations.

The advantage of a decreasing right-hand superiority: The influence of laterality on a selected musical skill (sight reading achievement)

In this study, the unrehearsed performance of music, known as 'sight reading', is used as a model to examine the influence of motoric laterality on highly challenging musical performance skills. As expertise research has shown, differences in this skill can be partially explained by factors such as accumulated practise and an early start to training. However, up until now, neurobiological factors that may influence highly demanding instrumental performance have been widely neglected. In an experiment with 52 piano students at a German university music department, we could show that the most challenging musical skill, sight reading (which is characterized by extreme demands on the performer's real time information processing), is positively correlated with decreasing right-hand superiority of performers. Laterality was measured by the differences between left and right-hand performance in a speed tapping task. SR achievement was measured using an accompanying task paradigm. An overall superiority of 22% for non-right-handed pianists was found. This effect is gender-related and stronger in non-right-handed males (r(24) = -0.49, p<0.05) than in non-right-handed females (r(28) = -0.16, p>0.05). We conclude that non-right-handed motoric laterality is associated with neurobiological advantages required for sight reading, an extremely demanding musical subskill.

Hand preference, practice order, and spatial assimilations in rapid bimanual movement

When subjects make rapid bimanual aiming movements over different distances, spatial assimilations are shown; the shorter distance limb overshoots when paired with a longer distance limb. Recent research has also shown spatial assimilations to be greater in the nonpreferred left limb of right-handed subjects, but it is not known whether the increased spatial assimilations represent a handedness effect or one of hemispheric lateralization of motor control. To determine the nature of the asymmetric effect, left- (n = 32) and right- (n = 60) handed subjects part practiced, then whole practiced, short (20 degrees ) and long 60 degrees ) reversal movements. During whole practice, both groups showed spatial assimilations in the shorter distance limb, particularly when the left limb performed the short movement. This asymmetry was greatest for right-handed subjects, but left-handed subjects showed smaller, but systematic effects, providing moderate support for the hypothesis that the asymmetric effect is due to hemispheric lateralization of motor control. All interlimb differences in spatial accuracy for the short and long movements were eliminated with practice, however, suggesting the asymmetric effect was temporary as well. In addition, subjects who part practiced the long movement just prior to whole practice showed greater overshooting in the short distance limb compared with subjects who followed the other practice order throughout whole practice and the no-KR retention trials. Such findings suggest that the part-practice order of bimanual tasks can directionally bias whole-task performance.

Temporal regularity of tapping by the left and right hands in timed and untimed finger tapping

The temporal characteristics of repetitive finger tapping by the left and right hands were examined in two experiments. In the first experiment, interresponse intervals (IRIs) were recorded while right-handed male subjects tapped in synchrony with an auditory timing pulse (the synchronization phase) and then attempted to maintain the same tapping rate without the timing pulses (the continuation phase). The left and right hands performed separately, at four different rates (interpulse intervals of 250, 500, 750, and 1500 ms). There was no asymmetry of the asynchronies of the timing pulses and the associated responses in the synchronization phase or of the IRIs in either phase, but there was an asymmetry of chronization phase or of the IRIs in either phase, but there was an asymmetry in the temporal dispersion of the responses in both phases. in the second experiment, right-handed males tapped separately with each hand at three different speeds: as quickly as possible, at a fast but steady rate, and at a slow rhythmical rate. The speed asymmetry present when tapping as quickly as possible (with the preferred hand tapping more quickly ) was reduced when tapping at the fast steady rate and was absent when tapping at the slow rhythmical rate. The temporal dispersion of the IRIs produced by the nonpreferred hand was greater than the temporal dispersion of those produced by the preferred hand in all speed conditions. These results show smaller temporal dispersion of tapping by the preferred hand in right-handed males under different conditions, including submaximal speeds at which both hands respond at the same rate. This suggests that the motor system controlling the preferred hand in right-handers had more precise timing of response output than that controlling the nonpreferred hand.

Reduced timing variability during bimanual coupling: a role for sensory information

On a repetitive tapping task, the within-hand variability of intertap intervals is reduced when participants tap with two hands as compared to one-hand tapping. Because this bimanual advantage can be attributed to timer variance (Wing-Kristofferson model, 1973a, b), separate timers have been proposed for each hand, whose outputs are then averaged (Helmuth & Ivry, 1996). An alternative notion is that action timing is based on its sensory reafferences (Aschersleben & Prinz, 1995; Prinz, 1990). The bimanual advantage is then due to increased sensory reafference. We studied bimanual tapping with the continuation paradigm. Participants first synchronized their taps with a metronome and then continued without the pacing signal. Experiment 1 replicated the bimanual advantage. Experiment 2 examined the influence of additional sensory reafferences. Results showed a reduction of timer variance for both uni- and bimanual tapping when auditory feedback was added to each tap. Experiment 3 showed that the bimanual advantage decreased when auditory feedback was removed from taps with the left hand. Results indicate that the sensory reafferences of both hands are used and integrated into timing. This is consistent with the assumption that the bimanual advantage is at least partly due to the increase in sensory reafference. A reformulation of the Wing-Kristofferson model is proposed to explain these results, in which the timer provides action goals in terms of sensory reafferences.

A performance measure of the degree of hand preference

The present paper describes a performance method for determining hand preference. The task requires participants to reach into different regions of hemispace to perform various actions (point, pick up, toss, sweep, and position) with a dowel located at each position. In accordance with the participants' hand preference as measured by the Waterloo Handedness Questionnaire, the preferred hand was used more frequently on the various performance tasks. The distribution of hand use in working space indicates that preferred hand use was almost exclusive for actions carried out in ipsilateral hemispace, while it is used only moderately for actions in contralateral hemispace, revealing that this hand is used throughout a wider range of extrapersonal space than the nonpreferred hand. These trends were observed across all of the performance tasks, suggesting that task complexity did not affect the frequency of preferred hand use either overall or, more specifically, in right hemispace, as was predicted. This finding is inconsistent with empirical work on questionnaires indicating that verbal reports of preferred hand use increase for more complex tasks (e.g., Steenhuis & Bryden, 1988). As well, performance on the preferential reaching task correlated significantly with hand preference as measured on the Waterloo Handedness Questionnaire (Bryden, 1977), unlike the other performance measure examined, indicating that the preferential reaching task is sensitive to differences in the degree of hand preference.

Predicting hand preference with performance on motor tasks

Handedness may be defined as preference or hand-differences in task performance. The strength and significance of the relationship between hand preference and hand performance asymmetries have been contested. To evaluate this relationship, we administered the Edinburgh Handedness Inventory and measured asymmetries in finger tapping, Purdue Pegboard, and grip strength in 30 subjects who prefer their right hand and 30 subjects who prefer their left hand. Hand asymmetries in finger tapping, Purdue Pegboard, and grip strength each predicted hand preference scores. However, a multiple regression equation best predicted hand preference by using performance of each task. Hand asymmetries in finger tapping correlated strongly with asymmetries in Purdue Pegboard performance, but neither of these asymmetries correlated strongly with asymmetries in grip strength. These findings indicate that hand preference and asymmetries in motor proficiency are strongly related, but suggest that preference and proficiency for different aspects of motor performance may be independently lateralized.

Comparative analysis of diadochokinetic movements

Tests of diadochokinesia are an inherent part of a neurological examination. Various quantifying methods have been proposed to increase the objectivity, sensitivity, and reliability of such examinations. The methods used and analyses performed, however, differ substantially between tasks. We used a three-dimensional, ultrasound-based recording device to continuously record joint angles during three diadochokinetic movements, avoiding any external constraints of the movements. Alternate pronation and supination of the forearm, tapping with the whole hand and with the index finger in isolation were analyzed in a sample of 63 healthy control subjects. The most sensitive measure for capturing effects of gender, sex, and active hand was frequency. The right hand was faster than the left in all tasks, tapping performance declined with increasing age, and male subjects were faster than females in forearm diadochokinesia. Other measures that characterize speed of movement such as maximum angular velocities and accelerations did not yield comparable sensitivity in detecting the same statistical effects. However, angular velocity achieved the highest test-retest reliability for forearm diadochokinesia, while frequency was reproduced in the tapping tasks. Additional measures characterizing symmetry of the angular velocity profiles and intraindividual variability were shown to be largely independent of movement speed. Examples in neurological patients showed that the data define a valuable standard against which pathological performance can be precisely evaluated. In addition, the different measures captured dissociable aspects of motor performance that may further help to characterize the deficit and adjust therapy.

The development of interlimb coordination during bimanual finger tapping

Normal subjects aged 7-25 years were asked to tap the index fingers of both hands: a) in four different patterns of interlimb coordination; b) at two different response frequencies; and c) both before and after the entraining metronome was turned off. The outcome variables of primary interest were the within-subject variability of interresponse intervals (IRI) as an index of timing precision; and deviations from prescribed response frequency, as an index of temporal tracking accuracy. Stability of timing precision and accuracy of temporal tracking increased significantly from 7 to 9 and from 9 to 11 years, with only minor advances thereafter. There were significant right-left performance asymmetries in all bimanual tasks; variability of IRI and deviations from prescribed rate were greater at the faster of the two response frequencies tested; and stability of IRI and accuracy of temporal tracking were greater with than without the metronome. Stability of IRI and accuracy of temporal tracking were strongly correlated in some bimanual tasks. The findings are discussed in terms of the two major theoretical perspectives on human brain-behavior relationships that have specifically addressed the issue of bimanual coordination.