How should we test infant handedness?

Early, concurrent, and consistent hand preferences predict stacking in toddlerhood

Stacking is a hallmark of fine motor skill development and requires skilled hand use. One mechanism for children to gain manual proficiency involves establishing a hand preference that creates practice differences between the hands as the preferred hand is used more often and in different ways than the other. Prior work found that stacking skill emerged earlier for infants with an identifiable hand preference. However, it is not known how hand preference relates to later toddler stacking performance. This study examined the effects of early hand preference (infant pattern), concurrent hand preference (toddler pattern), and consistent hand preference (infant to toddler pattern) on toddler stacking skills. Sixty-one toddlers, whose hand preferences as infants were known, were assessed for their toddler hand preference and their stacking skill across 7 monthly visits from 18 to 24 months of age. Using multilevel Poisson longitudinal analysis, children with hand preferences that were consistent across both infancy and toddlerhood were more successful at stacking, compared to those with inconsistent preferences across the infant and toddler periods. Thus, consistency of hand preferences during the first 2 years likely contributes toward individual differences in the development of fine motor skills.

Effect of Palmar Grasp Reflex Stimulation on Physiological Parameters and Crying Time During Neonatal Bath: A Randomized Controlled Trial

OBJECTIVE

This study aimed to determine the effect of palmar grasp reflex stimulation during a neonatal bath on the physiological parameters and crying time of the newborn.

DESIGN, SETTING, AND PARTICIPANTS

This study was designed as a parallel randomized clinical trial. Parents fully understood the study procedure at the Neonatal Intensive Care Unit in Turkey (N = 82). Both written and verbal consent was obtained from the parents. Newborns who were ineligible for tub bathing were excluded from the study. The babies in the control group were given baths according to the tub bathing standards. Babies in the experimental group were given palmar grasp reflex stimulation during the baths. The variables examined included body temperature, respiratory rate, pulse, oxygen saturation levels, and crying time. In all analyses, p < 0.05 was accepted as statistically significant.

RESULTS

The heart rate of the experimental group was 5.2 beats per minute slower than the control group (χ2 = 12.272; p < 0.001). The respiratory rate of the experimental group was 1.3 lower per minute compared to the control group (χ2 = 43.219; p < 0.001). In addition, the oxygen saturation level (%) of the experimental group was 0.4 higher than the control group (χ2 = 5.793; p < 0.016). Crying time was higher in the control group during bathing (p < 0.001).

CONCLUSION

The results showed that the palmar grasp reflex in newborn bathing helps to maintain the stability of physiological parameters and shortens the crying time of babies. Palmar grasp reflex stimulation is recommended in interventions that may cause stress.

Hand Movements in Communicative and Noncommunicative Situations in Very Young Infants: A Preliminary Study

As a step toward understanding the developmental relationship between handedness and language lateralization, this longitudinal study investigated how infants (N = 21) move their hands in noncommunicative and communicative situations at 2 weeks and at 3 months of age. The authors looked at whether left-right asymmetry in hand movements and in duration of self-touch appeared across conditions and whether the direction of asymmetry depended on the communicative nature of the situation. The authors found that asymmetries appeared less consistently than suggested in literature and did not only depend on the communicative nature of the situation. Instead, hand activity and self-touch patterns depended on age, the presence of the mother, the degree of novelty of the situation, and the presence of an object. The results partly support previous studies that pointed out an early differentiation of communicative hand movements versus noncommunicative ones in infants. It is in terms of the amount of global hand activity, rather than in those of the laterality of hand movements that this differentiation emerged in this study. At 3 months, infants moved their hands more in the communicative conditions than in the noncommunicative conditions and this difference appeared as a tendency already at 2 weeks of age.

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.

Right-handed one day, right-handed the next day?

Although a population bias toward right-hand preference is observed at the early stage of grasping, hand preference fluctuates in infancy. Given these fluctuations, one can wonder whether testing a young infant on a single occasion gives reliable results of its handedness. Very few studies have evaluated short-term test-retest reliability. This was the goal of this study in which 21 infants aged 9-15 months were tested for handedness every day for a total of 5 sessions. The infants were given a classical handedness baby test. Their handedness index (HI) and their category of handedness were compared across sessions. The results show that at the group level the distribution of handedness does not differ significantly across the five sessions. At the individual level, only 19% of infants were categorized as right-handed at all five sessions while 52.4% were consistent in using more one hand than the other across the five sessions (right hand: 47.6%). Most of the fluctuations across sessions occurred between being lateralized and non-lateralized rather than between being right-handed and left-handed. These figures indicate that testing handedness at that age gives fairly reliable results in terms of direction of hand preference, but less so in terms of degree.

The development of neuromotor skills and hand preference during infancy

Assessing infant handedness has been controversial. Different assessment techniques and theoretical approaches produce different results. Evidence from a dynamic systems perspective showed that the development of postural control during infancy affects the expression of an infant's handedness. However, others found that developmental changes in postural control influenced the amount of symmetrical (bimanual) reaching during infancy, but not hand preference. Since most studies of infant handedness use age to assess development, perhaps measures of an infant's developing neuromotor control, irrespective of age, would better predict changes in an infant's hand preference. To assess neuromotor development, items from [Touwen's (1976) Neurological development in infancy. Lavenham, Suffolk: The Lavenham Press, LTD]. "Group III" indices were used. These items assess developmental changes in neuromotor abilities throughout the 6-14-month age period. Hand preference for acquiring objects was measured during these same months. Group Based Trajectory Models (GBTM) of 380 infants identified four different groups of infants according to the trajectory of the development of their hand preferences (32% Early Right, 12% Early Left, 25% Late Right, 30% No Preference). A multilevel model was used to compare these four developmental trajectories according to age and neuromotor development. Age, not neuromotor development, is a better predictor of differences in developmental trajectories of the four hand preference groups. However, Late Right infants are significantly less developed at 6 months than No Preference, Early Right and Left infants and both Early Right and Left infants are most advanced at 6 months. All groups exhibit similar rates of neuromotor development indicating no "catch-up" by the Late Right infants. Thus, any assessment of infant handedness will incorporate necessarily four groups of infants with differently developing hand preferences and neuromotor abilities.