Hand selection for role‐differentiated bimanual manipulation in a beading task: An assessment of typically developing children

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.

How Age, Cognitive Function and Gender Affect Bimanual Force Control

Coordinated bimanual control depends on information processing in different intra- and interhemispheric networks that differ with respect to task symmetry and laterality of execution. Aging and age-related cognitive impairments, but also sex can have detrimental effects on connectivity of these networks. We therefore expected effects of age, cognitive function and sex on bimanual force coordination. We furthermore expected these effects to depend on the characteristics of the task (i.e., difficulty and symmetry). 162 right handed participants (19 younger adults [YA], 21–30 years, 9 females; 52 cognitively healthy older adults [HOA], 80–91 years, 32 females; and 91 older adults with mild cognitive impairments [MCI] 80–91 years, 37 females) performed isometric bimanual force control tasks that required following constant or alternating (cyclic sine-wave) targets and varied in symmetry, i.e., (i) constant symmetric, asymmetric [with constant left and alternating right (ii) or vice versa (iii)], (iv) alternating in- and (v) alternating antiphase (both hands alternating with 0° or 180° relative phase, respectively). We analyzed general performance (time on target), bimanual coordination as coupling between hands (linear correlation coefficient) and structure of variability (i.e., complexity measured through detrended fluctuation analysis). Performance and coupling strongly depended on task symmetry and executing hand, with better performance in symmetric tasks and in asymmetric tasks when the left hand produced a constant and the right hand an alternating force. HOA and MCI, compared to YA, showed poorer performance (time on target) and reduced coupling in in- and antiphase tasks. Furthermore, both groups of OA displayed less complex structure in alternating force production tasks, a marker of reduced control. In addition, we found strong sex effects with females displaying reduced coupling during in- and antiphase coordination and less complex variably structure in constant force production. Results of this study revealed strong effects of age, but also sex on bimanual force control. Effects depended strongly on task symmetry and executing hand, possibly due to different requirements in interhemispheric information processing. So far, we found no clear relationship between behavioral markers of bimanual force control and age-related cognitive decline (compared to healthy aging), making further investigation necessary.