Infants' hand preferences for actions and gestures

Early Lateralization of Gestures in Autism: Right-Handed Points Predict Expressive Language

Children with autism spectrum disorder (ASD) produce fewer deictic gestures, accompanied by delays/deviations in speech development, compared to typically-developing (TD) children. We ask whether children with ASD-like TD children-show right-hand preference in gesturing and whether right-handed gestures predict their vocabulary size in speech. Our analysis of handedness in gesturing in children with ASD (n = 23, M_age = 30-months) and with TD (n = 23, M_age = 18-months) during mother-child play showed a right-hand preference for TD children-but not for children with ASD. Nonetheless, right-handed deictic gestures predicted expressive vocabulary 1 year later in both children with ASD and with TD. Handedness for gesture, both hand preference and amount of right-handed pointing, may be an important indicator of language development in autism and typical development.

Measuring infant handedness reliably from reaching: A systematic review

Researchers have utilized reaching paradigms to measure infant handedness for more than a century. However, methods vary widely. Recent research has identified that the number of trials used in assessment is critical with the recommendation that at least 15 trials are necessary to reliably classify infants into handedness categories via statistical cutoffs. As a first step towards establishing best practices for the field, we identified, categorized, and synthesized findings according to trial number from studies that utilized reaching to index handedness in infants across the first two years of life using PRISMA guidelines. Database searches were conducted in PsycINFO, PubMed, and Ovid MEDLINE®. All articles published through May 2018 were included. Additional records were identified through other sources. After removing duplicates, 1,116 records were screened using the online software program Abstrackr. Of these records, 125 full-text articles were further assessed for eligibility, and 87 articles were included in the qualitative synthesis. Results revealed that the majority of papers published since 1890 (70%) do not meet the 15-trial minimum criterion for statistically reliable measurement of infant handedness. Broad themes from articles meeting the measurement criterion and implications for future research are discussed.

Human laterality for manipulation and gestural communication: A study of beach-volleyball players during the Olympic Games

Comparative studies can help understand better brain functional lateralization for manipulation and language. This study investigated and compared, for the first time, human adults' laterality for manipulation and gestures in a non-experimental social context. We analysed the manual laterality of 48 beach volleyball athletes for four frequently expressed behaviours: a complex throwing action (jump serve) and three gestures (CLAP HAND, PUMP FIST and SLAP HAND-TO-HAND). We evaluated population-level laterality bias for each of the four behaviours separately, compared manual laterality between behaviours and investigated factors influencing gestural laterality. We furthered our between-gestures comparison by taking into account three categories of factors simultaneously: gesture characteristics (sensory modality), interactional context components (positions of interactants and emotional valence), and individual demographic characteristics (age, sex and country). Our study showed that (1) each behaviour considered presented a population-level right-hand bias, (2) differences of laterality between behaviours were probably related to gesture sensory modality and (3) signaller's laterality was modulated differently in relation to positions of interactants, emotional valence, age and sex. Our results support the literature suggesting that left-hemisphere specialization for manipulation and language (speech and gestures) may have evolved from complex manual activities such as throwing and from gestural communication.

Assessment and analysis of human laterality for manipulation and communication using the Rennes Laterality Questionnaire

Despite significant scientific advances, the nature of the left-hemispheric systems involved in language (speech and gesture) and manual actions is still unclear. To date, investigations of human laterality focused mainly on non-communication functions. Although gestural laterality data have been published for infants and children, relatively little is known about laterality of human gestural communication. This study investigated human laterality in depth considering non-communication manipulation actions and various gesture types involving hands, feet, face and ears. We constructed an online laterality questionnaire including 60 items related to daily activities. We collected 317 594 item responses by 5904 randomly selected participants. The highest percentages of strong left-lateralized (6.76%) and strong right-lateralized participants (75.19%) were for manipulation actions. The highest percentages of mixed left-lateralized (12.30%) and ambidextrous (50.23%) participants were found for head-related gestures. The highest percentage of mixed right-lateralized participants (55.33%) was found for auditory gestures. Every behavioural category showed a significant population-level right-side bias. More precisely, participants were predominantly right-lateralized for non-communication manual actions, for visual iconic, visual symbolic, visual deictic (with and without speech), tactile and auditory manual gestures as well as for podial and head-related gestures. Our findings support previous studies reporting that humans have left-brain predominance for gestures and complex motor activities such as tool-use. Our study shows that the Rennes Laterality Questionnaire is a useful research instrument to assess and analyse human laterality for both manipulation and communication functions.

Early sign language acquisition and the development of hand preference in young children

Hand preference for signing and for nonsign actions was examined longitudinally in 24 young children (3 deaf, 21 hearing) with deaf parents. Most of these children showed a strong preference for their right hands in their sign production. This preference emerged early in their development, was relatively consistent over time, and predicted mature hand preference. Although most of the children also preferred to use their right hands in nonsign actions, their right-hand preference for signing was much stronger. Hand preference scores for two types of nonsign actions, communicative gestures and object actions, were significantly correlated with those for signing. Hand preference also was linked to rate of motor development but not to sign language acquisition. These findings are discussed with regard to current conceptualizations about the interrelationships among language, motor processes, and laterality.

Lateral asymmetries in infancy: implications for the development of the hemispheres

Cerebral asymmetry of cognitive processing of stimulus information is commonly viewed as a neocortical phenomenon. However, a number of lines of evidence give innate asymmetry of brainstem motivating systems, which anticipate experience, a key role. Spontaneous asymmetries of gesture and emotion can be observed in infants, who entirely lack language and visuo-constructive skills. Motives for communication in early life may direct subsequent development of complementary cognitive systems in left and right hemispheres. In split-brain monkeys, lateralized motive sets, intentions for manipulation by one hand, can determine which hemisphere will see and learn. Evolutionary antecedents of cerebral asymmetry appear to affect motivation, social signalling and bimanual coordination, with secondary effect in perceptual processing and learning. The hemispheres of adult humans differ in links with neurochemical system that regulate motor initiatives, exploration and attention, and the approach/withdrawal balance in social encounters. Asymmetries in emotional and communicative behaviour in infancy support evidence that an Intrinsic Motive Formation emerging in the embryo human brain stem regulates asymmetries in development and in functioning of the cerebral cortex.

Maternal influences on infant hand-use during play with toys

Infant hand-use preferences are related to mother's, but not father's, handedness. Since infants match mother's hand-use during toy play, maternal handedness can affect infant hand-use. Twenty-eight mother-infant pairs (14 left-handed and 14 right-handed infants but all right-handed mothers) were videotaped while playing with six toys on the infant's 7-, 9-, and 11-month birthdays. Play was analyzed for five kinds of hand-use biasing situations, but maternal hand-use was the dominant influence. Infant matching of maternal hand-use increased with age and right-handed infants and female infants matched maternal hand-use more frequently. Concordance of hand-use preference between mother and infant seemed to account for both the matching and the stronger preferences of the right-handed compared to the left-handed infants.

Five-month-old girls' and boys' exploratory behaviors in the presence of familiar and unfamiliar toys

The exploratory behaviors of 60 5-month-old girls and boys were observed as they played with three unfamiliar toys and one familiar toy of their own during a laboratory session. Infants were seated at a table on the lap of an assistant. Each toy was placed on the table and remained there for 2 min after the infant first touched it. Frequency and duration of visual fixation on the toy, hand contact with the toy, five categories of lateralization, and eight categories of handling behaviors were measured. On the whole, the exploratory behaviors of girls and boys were not markedly different. However, girls spent more time than boys did in simultaneous hand contact with and visual fixation on their own familiar toy, whereas boys made more frequent contact with the familiar toy without visual fixation. In addition, boys displayed, overall, more tapping behaviors, and girls, more pinching and object-displacement behaviors. Girls and boys did not differ in manual lateralization. Results are discussed in reference to infants' rate of development, motor activity level, and girls' and boys' reactions to novelty.