The Effect of Explicit Cultural Bias on Lateral Preferences in Tunisia

Influence of target location, task complexity, and gender on children's use of their preferred foot

The goal of the present study was to compare the choice of foot of right-footed children with varying strengths of foot preference when performing two tasks of different levels of complexity at three spatial locations. 30 right-footed children were tested. The results showed that the general tendency to use one's preferred foot to interact with an object is more or less pronounced depending on the object's location and the complexity of the task. The children used their non-preferred left foot more often during the simple task and when the object was presented to the left. Our findings also revealed interactions between gender, age, and spatial location. At five, girls used globally less their left foot than boys. In addition, girls used their preferred right foot more frequently than boys when the object was presented to the left. Based on these results, it can be concluded that foot selection depends on foot preference, task demand, environmental context, and biological factors associated with motor dominance.

Beyond handedness: assessing younger adults and older people lateral preference in six laterality dimensions

Lateral preference is influenced by many different factors. Although studies that assessed handedness contributed greatly to our understanding of the phenomenon, looking to other dimensions of motor laterality, such as lower limbs, trunk, visual and hearing preference, may be an interesting strategy to further advance in the field. Comparing different age groups with a complete inventory also contributes to understanding the ageing impact on these variables. Our aim, therefore, was to assess six motor laterality dimensions in younger adults and older people. Two hundred subjects participated in this study (102 adults, 30.6 ± 11.2 years old, and 98 elders, 70.4 ± 7.22 years old) and lateral preference was assessed by the Global Lateral Preference Inventory. We verified significant differences between groups in all dimensions, except the visual one, with proportionally stronger right preference in the older group. Compared to other dimensions, higher frequency of ambidexterity was observed in trunk, hearing and visual preference for both groups. These results might indicate that lateral preference is, indeed, multifactorial, being affected by ageing, task complexity and other possible related aspects.

Can Population-Level Laterality Stem from Social Pressures? Evidence from Cheek Kissing in Humans

Despite extensive research, the origins and functions of behavioural laterality remain largely unclear. One of the most striking unresolved issues is the fact that laterality generally occurs at the population-level. Why would the majority of the individuals of a population exhibit the same laterality, while individual-level laterality would yet provide the advantages in terms of improving behavioural efficiency? Are social pressures the key factor? Can social pressures induce alignment of laterality between the individuals of a population? Can the effect of social pressures overpass the effect of other possible determining factors (e.g. genes)? We tested this important new hypothesis in humans, for the first time. We asked whether population-level laterality could stem from social pressures. Namely, we assessed social pressures on laterality in an interactive social behaviour: kissing on the cheek as a greeting. We performed observations in 10 cities of France. The observations took place in spots where people of the city meet and greet each other. We showed that: a) there is a population-level laterality for cheek kissing, with the majority of individuals being aligned in each city, and b) there is a variation between populations, with a laterality that depends on the city. These results were confirmed by our complementary data from questionnaires and internet surveys. These findings show that social pressures are involved in determining laterality. They demonstrate that population-level laterality can stem from social pressures.

Forelimb preferences in human beings and other species: multiple models for testing hypotheses on lateralization

Functional preferences in the use of right/left forelimbs are not exclusively present in humans but have been widely documented in a variety of vertebrate and invertebrate species. A matter of debate is whether non-human species exhibit a degree and consistency of functional forelimb asymmetries comparable to human handedness. The comparison is made difficult by the variability in hand use in humans and the few comparable studies conducted on other species. In spite of this, interesting continuities appear in functions such as feeding, object manipulation and communicative gestures. Studies on invertebrates show how widespread forelimb preferences are among animals, and the importance of experience for the development of forelimb asymmetries. Vertebrate species have been extensively investigated to clarify the origins of forelimb functional asymmetries: comparative evidence shows that selective pressures for different functions have likely driven the evolution of human handedness. Evidence of a complex genetic architecture of human handedness is in line with the idea of multiple evolutionary origins of this trait.

How space-number associations may be created in preliterate children: six distinct mechanisms

The directionality of space-number association (SNA) is shaped by cultural experiences. It usually follows the culturally dominant reading direction. Smaller numbers are generally associated with the starting side for reading (left side in Western cultures), while larger numbers are associated with the right endpoint side. However, SNAs consistent with cultural reading directions are present before children can actually read and write. Therefore, these SNAs cannot only be shaped by the direction of children’s own reading/writing behavior. We propose six distinct processes – one biological and five cultural/educational – underlying directional SNAs before formal reading acquisition: (i) Brain lateralization, (ii) Monitoring adult reading behavior, (iii) Pretend reading and writing, and rudimentary reading and writing skills, (iv) Dominant attentional directional preferences in a society, not directly related to reading direction, (v) Direct spatial-numerical learning, (vi) Other spatial-directional processes independent of reading direction. In this mini-review, we will differentiate between these processes, elaborate when in development they might emerge, discuss how they may create the SNAs observed in preliterate children and propose how they can be studied in the future.

Looking at eye dominance from a different angle: is sighting strength related to hand preference?

Sighting dominance (the behavioural preference for one eye over the other under monocular viewing conditions) has traditionally been thought of as a robust individual trait. However, Khan and Crawford (2001) have shown that, under certain viewing conditions, eye preference reverses as a function of horizontal gaze angle. Remarkably, the reversal of sighting from one eye to the other depends on which hand is used to reach out and grasp the target. Their procedure provides an ideal way to measure the strength of monocular preference for sighting, which may be related to other indicators of hemispheric specialisation for speech, language and motor function. Therefore, we hypothesised that individuals with consistent side preferences (e.g., right hand, right eye) should have more robust sighting dominance than those with crossed lateral preferences. To test this idea, we compared strength of eye dominance in individuals who are consistently right or left sided for hand and foot preference with those who are not. We also modified their procedure in order to minimise a potential image size confound, suggested by Banks et al. (2004) as an explanation of Khan and Crawford's results. We found that the sighting dominance switch occurred at similar eccentricities when we controlled for effects of hand occlusion and target size differences. We also found that sighting dominance thresholds change predictably with the hand used. However, we found no evidence for relationships between strength of hand preference as assessed by questionnaire or by pegboard performance and strength of sighting dominance. Similarly, participants with consistent hand and foot preferences did not show stronger eye preference as assessed using the Khan and Crawford procedure. These data are discussed in terms of indirect relationships between sighting dominance, hand preference and cerebral specialisation for language and motor control.

A valid and reliable clinical determination of footedness

OBJECTIVE

To develop a valid and reliable clinical performance measure of foot dominance.

DESIGN

Prospective cross-sectional study with repeated measures.

SETTING

Laboratory.

PARTICIPANTS

A total of 175 healthy male and female subjects ages 16 to 37 years.

INTERVENTIONS

A total of 12 lower limb functional performance skilled and unskilled tasks.

MAIN OUTCOME MEASURE

Internal consistency and reliability of selected measures.

RESULTS

Principal components factor analysis with varimax rotation resulted in tasks being grouped into 3 components with Eigen values greater than 1, which explained 55% of the variance. An inventory of 4 skilled component tasks was found to reliably determine footedness. Internal consistency derived from Cronbach's alpha produced a value of 0.819 for the skilled tasks. Three of the 4 skilled tasks were found to have excellent reliability (>0.75) with almost perfect agreement.

CONCLUSIONS

Determining foot dominance is important in a rehabilitation setting, considering the normal laterality variation in cerebral hemisphere function, limb morphology, and motor performance parameters encountered in humans. This study developed an inventory of skilled performance tasks to reliably determine footedness. Four bilateral tasks were identified that had excellent test-retest reliability and high internal consistency and are recommended as global determinants of footedness.

The influence of classical dance training on preferred supporting leg and whole body turning bias

A rightward turning bias has been more frequently noted during adult classical dance practice than during spontaneous rotations. Training could play a role in inducing a preferred direction. We observed the preferred direction for executing four spontaneous whole-body full turns (pirouettes), with eyes open or closed, in pre-pubertal untrained girls and classical dance students. Of untrained girls, 58% showed a leftward turning bias (LTB) and 42% a rightward turning bias (RTB), independently of vision, lateral preferences, and supporting leg. Only one dancer showed a consistent LTB while the majority showed a RTB, with a tendency to use the left leg to turn towards the right. These results suggest that the role of the vestibular and visual systems is minimal for untrained girls, and suggest a training influence for dancers. The dance students' choice of a supporting leg for turning may exploit some biomechanical properties facilitating the pirouette.

Laterality in persons with intellectual disability II. Hand, foot, ear, and eye laterality in persons with Trisomy 21 and Williams-Beuren syndrome

Laterality (hand, foot, ear, and eye) was assessed in participants with Trisomy 21 (62) and Williams-Beuren syndrome (WBS) (39). Handedness was also assessed in a card reaching task. The comparison group included 184 typically developing persons. Two independent age sub-groups were formed: 7 to 10 years old and 11 to 34 years old. We confirmed previous data: individuals with T21 were more frequently left- or mixed-handed than typically developing persons; individuals with WBS had intermediate scores. The two groups with genetic disorders had less right foot preference. Manual and foot inconsistencies characterized both groups with genetic disorders. Cross hand-foot preference was lower in the typically developing group. Differences in IQ levels did not correlate with differences in laterality scores. Overall laterality profiles were not the same in the two groups with genetic disorders: the greatest differences were observed between typically developing persons and persons with Trisomy 21.