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

Neuroanatomical correlates of musicianship in left-handers

BACKGROUND

Left-handedness is a condition that reverses the typical left cerebral dominance of motor control to an atypical right dominance. The impact of this distinct control - and its associated neuroanatomical peculiarities - on other cognitive functions such as music processing or playing a musical instrument remains unexplored. Previous studies in right-handed population have linked musicianship to a larger volume in the (right) auditory cortex and a larger volume in the (right) arcuate fasciculus.

RESULTS

In our study, we reveal that left-handed musicians (n = 55), in comparison to left-handed non-musicians (n = 75), exhibit a larger gray matter volume in both the left and right Heschl's gyrus, critical for auditory processing. They also present a higher number of streamlines across the anterior segment of the right arcuate fasciculus. Importantly, atypical hemispheric lateralization of speech (notably prevalent among left-handers) was associated to a rightward asymmetry of the AF, in contrast to the leftward asymmetry exhibited by the typically lateralized.

CONCLUSIONS

These findings suggest that left-handed musicians share similar neuroanatomical characteristics with their right-handed counterparts. However, atypical lateralization of speech might potentiate the right audiomotor pathway, which has been associated with musicianship and better musical skills. This may help explain why musicians are more prevalent among left-handers and shed light on their cognitive advantages.

The painter who changed her brain at the flick of a switch

The study of artists with acquired brain damage is an empirical way to investigate the multiplicity of cerebral changes that occur with artistic training. We describe a talented painter with a left progressive cerebral lesion. In spite of losing function of her right hand, she regained dexterity of the left one in ten days for painting and drawing but not for writing. We discuss two potential explanations for her rapid recovery: (a) her extensive artistic training and/or (b) the slow-growing nature of her cerebral lesion.

Personality, learning styles and handedness: The use of the non-dominant hand in pre-clinical operative dentistry training

AIM

This research was undertaken with the aim of using personality traits, learning styles and handedness to develop and evaluate a scale to measure a new concept in operative dentistry, symmetrisation. An initial hypothesis was proposed, stating that handedness, personality trait and learning style could be used to predict symmetrisation potential in the domain of operative dentistry.

METHODS

Participants completed three questionnaires: the Edinburgh handedness inventory assessment; the Keirsey Temperament Sorter-II (KTS-II); and the learning style assessment (VARK). Then, participants prepared a cavity on an artificial third molar tooth in the traditional phantom head using their non-dominant hand. For evaluation and comparison purposes, Standard Tessellation Language images were obtained from prepared teeth using a CAD/CAM scanner and then aligned against a reference "unprepared" tooth image using a custom software developed by the authors based on the Iterative Closest Point algorithm.

RESULTS

Extroverts, intuitive and participants characterised as relying on their feelings were more accurate compared to introverts, sensory and toughminded participants, respectively. Extroverts were faster to complete the task compared to introverts. Participants with a preference for read/writing learning style produced more errors than any of the other groups. Handedness, however, did not show any significant association with performance.

CONCLUSIONS

It was concluded that both the KTS-II and the learning style assessment (VARK) questionnaires possess potential as useful measures of symmetrisation potential and the ability to use the non-dominant hand in operative dentistry, as well as platform for continuing research.

Influence of musical background on surgical skills acquisition

BACKGROUND

There is growing interest in identifying trainees with surgical aptitude predictive of eventual technical proficiency. Musical tasks involve complex, cerebral activity, and ambidextrousity, which may have a positive impact on the acquisition of surgical skill sets. The purpose of this study was to investigate the influence of prior musical experience on the performance of basic surgical skills.

METHODS

This was a prospective cross-sectional study involving 51 novice undergraduate and medical school trainees with no prior surgical exposure. Musicality was assessed with a detailed survey and objectively with the Mini-Profile of Music Perception Skills test. Dexterity was assessed using the Purdue Pegboard test. Surgical skills were then evaluated by performing 2 timed suturing trials after observing tutorial video, followed by a timed laparoscopic peg transfer test. Outcomes included both speed and quality of performance.

RESULTS

Participants with prior musical experience performed better than nonmusicians on the Mini-Profile of Music Perception Skills test (P = .015), dominant hand dexterity (P = .05), suture quality (P < .03), and laparoscopic peg transfer speed (P < .01). There was no significant difference in the suturing speed between musicians and nonmusicians. The dexterity and Mini-Profile of Music Perception Skills scores were predictive of suture quality (P < .01). Among musicians, duration of musical training, inactivity, instrument type, and certification levels did not correlate with differences in surgical task performance.

CONCLUSION

Musical background is associated with better performance of fundamental surgical skills among surgical novices, particularly technique quality. Although this does not imply superior ultimate surgical ability, musicality may be a marker for basic surgical skill development useful in identifying suitable candidates for surgical training.

Left-handed musicians show a higher probability of atypical cerebral dominance for language

Music processing and right hemispheric language lateralization share a common network in the right auditory cortex and its frontal connections. Given that the development of hemispheric language dominance takes place over several years, this study tested whether musicianship could increase the probability of observing right language dominance in left-handers. Using a classic fMRI language paradigm, results showed that atypical lateralization was more predominant in musicians (40%) than in nonmusicians (5%). Comparison of left-handers with typical left and atypical right lateralization revealed that: (a) atypical cases presented a thicker right pars triangularis and more gyrified left Heschl's gyrus; and (b) the right pars triangularis of atypical cases showed a stronger intra-hemispheric functional connectivity with the right angular gyrus, but a weaker interhemispheric functional connectivity with part of the left Broca's area. Thus, musicianship is the first known factor related to a higher prevalence of atypical language dominance in healthy left-handed individuals. We suggest that differences in the frontal and temporal cortex might act as shared predisposing factors to both musicianship and atypical language lateralization.

Individual differences in musical training and executive functions: A latent variable approach

Learning and performing music draw on a host of cognitive abilities, and previous research has postulated that musicians might have advantages in related cognitive processes. One such aspect of cognition that may be related to musical training is executive functions (EFs), a set of top-down processes that regulate behavior and cognition according to task demands. Previous studies investigating the link between musical training and EFs have yielded mixed results and are difficult to compare. In part, this is because most studies have looked at only one specific cognitive process, and even studies looking at the same process have used different experimental tasks. Furthermore, most correlational studies have used different "musician" and "non-musician" categorizations for their comparisons, so generalizing the findings is difficult. The present study provides a more comprehensive assessment of how individual differences in musical training relate to latent measures of three separable aspects of EFs. We administered a well-validated EF battery containing multiple tasks tapping the EF components of inhibition, shifting, and working memory updating (Friedman et al. in Journal of Experimental Psychology: General, 137, 201-225, 2008), as well as a comprehensive, continuous measure of musical training and sophistication (Müllensiefen et al., in PLoS ONE, 9, e89642, 2014). Musical training correlated with some individual EF tasks involving inhibition and working memory updating, but not with individual tasks involving shifting. However, musical training only predicted the latent variable of working memory updating, but not the latent variables of inhibition or shifting after controlling for IQ, socioeconomic status, and handedness. Although these data are correlational, they nonetheless suggest that musical experience places particularly strong demands specifically on working memory updating processes.

Motor Lateralization May Be Influenced by Long-Term Piano Playing Practice

Motor lateralization is viewed as anatomical or functional asymmetry of the two sides of the body. Functional motor asymmetry can be influenced by musical practice. This study explored whether piano playing experience modulates motor asymmetry and leads to an altered pattern of hand selection, reflecting an altered handedness. We asked two groups of right-handed participants-piano players and non-piano players-to reach targets in their frontal space with both arms, and we tested the motor performance of each arm on this task and then on an arm preference test. As musical practice can decrease motor asymmetry between arms, we hypothesized that participants with piano playing experience would display less interlimb asymmetry and that this, in turn, would change their arm preference pattern, compared with participants without piano playing experience. We found support for both hypotheses, and we conclude that arm selection (preference) is not biologically fixed, but, rather, can be modulated through long-term piano playing.

The effect of handedness on spatial and motor representation of pitch patterns in pianists

This study investigated the effect of handedness on pianists' abilities to adjust their keyboard performance skills to new spatial and motor mappings. Left- and right-handed pianists practiced simple melodies on a regular MIDI piano keyboard (practice) and were then asked to perform these with modified melodic contours (the same or reversed melodic contour causing a change of fingering) and on a reversed MIDI piano keyboard (test). The difference of performance duration between the practice and the test phase as well as the amount of errors played were used as test measures. Overall, a stronger effect for modified melodic contours than for the reversed keyboard was observed. Furthermore, we observed a trend of left-handed pianists to be quicker and more accurate in playing melodies when reversing their fingering with reversed contours in their left-hand performances. This suggests that handedness may influence pianists' skill to adjust to new spatial and motor mappings.

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.

The Relationship between Handedness and Mathematics Is Non-linear and Is Moderated by Gender, Age, and Type of Task

The relationship between handedness and mathematical ability is still highly controversial. While some researchers have claimed that left-handers are gifted in mathematics and strong right-handers perform the worst in mathematical tasks, others have more recently proposed that mixed-handers are the most disadvantaged group. However, the studies in the field differ with regard to the ages and the gender of the participants, and the type of mathematical ability assessed. To disentangle these discrepancies, we conducted five studies in several Italian schools (total participants: N = 2,314), involving students of different ages (six to seventeen) and a range of mathematical tasks (e.g., arithmetic and reasoning). The results show that (a) linear and quadratic functions are insufficient for capturing the link between handedness and mathematical ability; (b) the percentage of variance in mathematics scores explained by handedness was larger than in previous studies (between 3 and 10% vs. 1%), and (c) the effect of handedness on mathematical ability depended on age, type of mathematical tasks, and gender. In accordance with previous research, handedness does represent a correlate of achievement in mathematics, but the shape of this relationship is more complicated than has been argued so far.

Tuning the mind: Exploring the connections between musical ability and executive functions

A growing body of research suggests that musical experience and ability are related to a variety of cognitive abilities, including executive functioning (EF). However, it is not yet clear if these relationships are limited to specific components of EF, limited to auditory tasks, or reflect very general cognitive advantages. This study investigated the existence and generality of the relationship between musical ability and EFs by evaluating the musical experience and ability of a large group of participants and investigating whether this predicts individual differences on three different components of EF - inhibition, updating, and switching - in both auditory and visual modalities. Musical ability predicted better performance on both auditory and visual updating tasks, even when controlling for a variety of potential confounds (age, handedness, bilingualism, and socio-economic status). However, musical ability was not clearly related to inhibitory control and was unrelated to switching performance. These data thus show that cognitive advantages associated with musical ability are not limited to auditory processes, but are limited to specific aspects of EF. This supports a process-specific (but modality-general) relationship between musical ability and non-musical aspects of cognition.

In praise of ambidexterity: How a continuum of handedness predicts social adjustment

This paper estimates the relationship between handedness and social adjustment in children. In addition to binary measures of hand preference, we also use a continuous measure of relative hand skill. Outcomes at ages 7, 11 and 16 are studied. The data used is the British 1958 Birth. Using a partially linear semi-parametric regression estimator, it is shown that non-right-handedness (as hand preference) is associated with poorer social adjustment but this effect weakens as individuals age into their teens. The continuous measure of hand skill has a non-monotonic effect on social adjustment with poorer social adjustment in the tails of the continuum. The results are consistent with a growing body of evidence which shows that it is the consistency or degree of laterality (rather than direction) that is important for many outcomes.

Increased cortical thickness and altered functional connectivity of the right superior temporal gyrus in left-handers

Altered structure in the temporal cortex has been implicated in the variable language laterality of left-handers (LH). The neuroanatomy of language lateralization and the corresponding synchronous functional connectivity (FC) in handedness cohorts are not, however, fully understood. We used structural and resting-state functional magnetic resonance imaging (fMRI) data to investigate the effect of altered cortical thickness on FC in LH and right-handers (RH). Whole-brain cortical thickness was calculated and compared between the LH and RH. We observed increased cortical thickness in the right superior temporal gyrus (STG) in the LH. A further FC analysis was conducted between the right STG and the remaining voxels in the brain. Compared with RH, the LH showed significantly higher FC in the left STG, right occipital cortex, and lower FC in the left inferior frontal gyrus and supramarginal gyrus. Our findings suggest that LH have atypical connectivity in the language network, with an enhanced role of the STG, findings which provide novel insights into the structural and functional substrates underlying the atypical language development of left-handed individuals.

The influence of deliberate practice on musical achievement: a meta-analysis

Deliberate practice (DP) is a task-specific structured training activity that plays a key role in understanding skill acquisition and explaining individual differences in expert performance. Relevant activities that qualify as DP have to be identified in every domain. For example, for training in classical music, solitary practice is a typical training activity during skill acquisition. To date, no meta-analysis on the quantifiable effect size of deliberate practice on attained performance in music has been conducted. Yet the identification of a quantifiable effect size could be relevant for the current discussion on the role of various factors on individual difference in musical achievement. Furthermore, a research synthesis might enable new computational approaches to musical development. Here we present the first meta-analysis on the role of deliberate practice in the domain of musical performance. A final sample size of 13 studies (total N = 788) was carefully extracted to satisfy the following criteria: reported durations of task-specific accumulated practice as predictor variables and objectively assessed musical achievement as the target variable. We identified an aggregated effect size of r c = 0.61; 95% CI [0.54, 0.67] for the relationship between task-relevant practice (which by definition includes DP) and musical achievement. Our results corroborate the central role of long-term (deliberate) practice for explaining expert performance in music.

Understanding left-handedness

BACKGROUND

The human cerebrum is asymmetrical, consisting of two hemispheres with differing functions. Recent epidemiological and neurobiological research has shed new light on the development of the cerebral lateralization of motor processes, including handedness. In this article, we present these findings from a medical perspective.

METHOD

We selectively searched the PubMed online database for articles including the terms "handedness," "left handedness," "right handedness," and "cerebral lateralization." Highly ranked and commonly cited articles were included in our analysis.

RESULTS

The emergence of handedness has been explained by physiological and pathological models. Handedness arose early in evolution and has probably been constitutive for the development of higher cognitive functions. For instance, handedness may have provided the basis for the development of speech and fine motor skills, both of which have played a critical role in the evolution of mankind. The disadvantages of certain types of handedness are discussed, as some cases seem to be associated with disease.

CONCLUSION

The consideration of handedness from the epidemiological, neurobiological, and medical points of view provides insight into cerebral lateralization.

Effect of handedness on the Stroop Colour Word Task

Handedness is associated with cerebral organisation, but its relationship with cognition remains unclear. Since the Stroop task is believed to measure aspects of executive control, this study aims to investigate the effect of handedness on Stroop interference. We used the Stroop task with 90 young adults with university education, of whom 47 (23 males) were right-handed and 43 (21 males) were left-handed. Main dependent variables were Stroop baseline (SB), Stroop incongruent (SI), and the proportional derivative Stroop reduction (SR) [SR=(SB - SI)/SB×100%] (Bugg, Delosh, Davalos, & Davis, 2007; Graf, Uttl, &Tuokko, 1995) scores. The analysis revealed that SI is significantly affected by both handedness and the interaction of sex×handedness, whereas SR is only affected by handedness. After controlling for the effect of SB on SI, only the effect of handedness remained statistically significant [F(1, 83) = 6.44, p=.013]. Post-hoc comparisons showed that left-handed females performed significantly better than right-handed females on both SI (p=.003) and SR (p=.007). The data suggest that handedness is associated with cognitive function alterations, which lead to a smaller Stroop interference of left-handers irrespectively of sex, an effect that is more pronounced in the female subpopulation.

Why are some people left-handed? An evolutionary perspective

Since prehistoric times, left-handed individuals have been ubiquitous in human populations, exhibiting geographical frequency variations. Evolutionary explanations have been proposed for the persistence of the handedness polymorphism. Left-handedness could be favoured by negative frequency-dependent selection. Data have suggested that left-handedness, as the rare hand preference, could represent an important strategic advantage in fighting interactions. However, the fact that left-handedness occurs at a low frequency indicates that some evolutionary costs could be associated with left-handedness. Overall, the evolutionary dynamics of this polymorphism are not fully understood. Here, we review the abundant literature available regarding the possible mechanisms and consequences of left-handedness. We point out that hand preference is heritable, and report how hand preference is influenced by genetic, hormonal, developmental and cultural factors. We review the available information on potential fitness costs and benefits acting as selective forces on the proportion of left-handers. Thus, evolutionary perspectives on the persistence of this polymorphism in humans are gathered for the first time, highlighting the necessity for an assessment of fitness differences between right- and left-handers.

Is left-handedness associated with a more pronounced age-related cognitive decline?

The effect of handedness on cognitive functioning has been the subject of much controversy. The influential "pathological left-handedness theory" posited by Coren and Halpern (1991) claims that left-handedness is probabilistically related to deviations from the neurological and cognitive norm. Many studies have failed to find negative effects of left-handedness on cognitive functioning, but most of these studies related handedness to cognition at one moment in time. Such studies do not exclude the possibility that sinistrality may be related to a more pronounced age-related longitudinal decline in cognitive functions. This hypothesis was tested in the present study. In a longitudinal study involving a large population sample of cognitively intact people aged at least 50 years at baseline, we evaluated the effect of handedness on age-related decline in four major cognitive domains: speed of information processing, verbal learning, long-term verbal memory, and executive functioning. The results failed to provide support for the hypothesis that sinistrality is associated with a more pronounced age-related cognitive decline. Recommendations for future studies are provided.

Amusia is associated with deficits in spatial processing

Amusia (commonly referred to as tone-deafness) is a difficulty in discriminating pitch changes in melodies that affects around 4% of the human population. Amusia cannot be explained as a simple sensory impairment. Here we show that amusia is strongly related to a deficit in spatial processing in adults. Compared to two matched control groups (musicians and non-musicians), participants in the amusic group were significantly impaired on a visually presented mental rotation task. Amusic subjects were also less prone to interference in a spatial stimulus-response incompatibility task and performed significantly faster than controls in an interference task in which they were required to make simple pitch discriminations while concurrently performing a mental rotation task. This indicates that the processing of pitch in music normally depends on the cognitive mechanisms that are used to process spatial representations in other modalities.