Ontogenetic constraints on the evolution of right-handedness.

Ontogenetic factors constrain the evolution of species-typical traits. Because human infants are born “prematurely” relative to other pri- mates, the development of handedness during infancy can reveal impor- tant ontogenetic influences on handedness that may have contributed to the evolution of the human species-typical trait of a population-level right- hand dominance

Concordance of Handedness Between Teacher and Student Facilitates Learning Manual Skills

Eighty-six left- and right-handed male and female adults received demonstrations of the manual actions involved in tying three different knots from either left- or right-handed female instructors. Learning was greatly facilitated by concordance of handedness between teacher and student, Sex of subject had no effect, nor were any interaction effects significant. Therefore, it is conceivable that observation learning of manual skill, which accompanied the hominid evolution of tool-use and tool-making skills, could have provided selective pressure for concordance (the right-bias) in human handedness

Intermanual transfer of tactile discrimination.

Little is known about infant tactile discrimination, even though most sensory and motor innervation of each and is ,restricted to the contralateral hemisphere

Postural Influences on the Development of Infant Lateralized and Symmetric Hand-Use

Within-individual variability is such an apparent characteristic of infant handedness that handedness is believed to consolidate only in childhood. Research showed that manifest handedness is influenced by emerging postural skills (sitting, crawling, and walking). In this investigation, it was proposed that symmetric hand-use (tendency to acquire objects bimanually), rather than lateralized hand-use (the use of one hand more than the other), may be influenced by postural changes. Trajectories of lateralized and symmetric hand-use for object acquisition were examined in 275 infants tested monthly from 6 to 14 months. Multilevel modeling revealed that change in lateralized hand-use is unrelated to developmental transitions in infant posture, whereas the trajectory of symmetric hand-use changes significantly with the development of postural skills

The effect of certain task characteristics on performance on two neuropsychological tests of spatial abilites.

Certain neuropsychological assessments of spatial ability assume that the processing of diagonality and nondiagonality of patterns is equivalent and that processing 2-D representations is equivalent to processing 3-D objects. The Stick Test and the Locomotor Maze Test also assume that successful performance requires the use of mental rotation. Normal adult subjects received either 2-D or 3-D versions of the Stick Test (n = 45) or an unlabeled or labeled version of the maze test (n = 25). Both tests used either nondiagonal or diagonal patterns. More errors were made on 2-D representations of sticks than on the 3-D sticks. Also, more errors occurred with the diagonal than with the orthogonal patterns on both tasks. When maze paths were labeled, fewer subjects made errors on the orthogonal paths than on the diagonal paths. Few subjects reported using mental rotation to perform these tasks. The performance of normal adults may violate the assumptions usually made about a test,s measure of spatial ability

A developmental psychobiological approach to developmental neuropsychology.

Although both developmental psychobiology and developmental neuropsychology examine the interface between biological and psychological processes, they differ in conceptual framework. This article argues for the incorporation into developmental neuropsychology of certain aspects of the conceptual framework of developmental psychobiology. Three principles of dynamic psychobiological interaction are described and applied to four issues in neuropsychology (handedness, sex differences in behavior, critical periods, and modularity of structure–function relations). Then, it is proposed that developmental psychobiology can make four direct contributions to developmental neuropsychology. Finally, it is argued that the value of the conceptual framework provided by developmental psychobiology depends, in part, on how well it translates into procedures that can be applied in the clinical settings of the developmental neuropsychologist

What is embodied: "A-not-B error" or delayed-response learning?

The procedures used to ensure reliable occurrences of the A- not-B error distort and miss essential features of Piaget’s original observa- tions. A model that meshes a mental event, highly restricted by testing pro- cedures, to the dynamics of bodily movement is of limited value. To embody more than just perseverative reaching, the formal model must in- corporate Piaget’s essential features

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

Infant Hand Preference and the Development of Cognitive Abilities

Hand preference develops in the first two postnatal years with nearly half of infants exhibiting a consistent early preference for acquiring objects. Others exhibit a more variable developmental trajectory but by the end of their second postnatal year, most exhibit a consistent hand preference for role-differentiated bimanual manipulation. According to some forms of embodiment theory, these differences in hand use patterns should influence the way children interact with their environments, which, in turn, should affect the structure and function of brain development. Such early differences in brain development should result in different trajectories of psychological development. We present evidence that children with consistent early hand preferences exhibit advanced patterns of cognitive development as compared to children who develop a hand preference later. Differences in the developmental trajectory of hand preference are predictive of developmental differences in language, object management skills, and tool-use skills. As predicted by Casasanto’s body-specificity hypothesis, infants with different hand preferences proceed along different developmental pathways of cognitive functioning

A meta-analysis of primate hand preference for reaching and other hand-use preferences.

Humans, as do most vertebrate species studied, exhibit a limb preference for unimanual activities. However, two characteristics of the human limb preference are thought to distinguish it from that of other vertebrates: (a) The preference is the same across a variety of manual tasks that have few task demands or motor skills in common (handedness consistency); and (b) the handedness consistency is unevenly distributed in the population with a distinct right-handed skew. Thus, depending on the criteria used to define a preference, 70%–90% of humans exhibit a consistent right-hand preference for manual activities (Annett, 1985). This sharp population bias in the distribution of hand preference has been prevalent for much of the natural history of humans (Corballis, 1991) and is present in all cultures (Annett, 1985). Anthropological evidence suggests a population bias toward right-handedness in the hominid ancestors of humans that dates back at least 1.8 million years (McManus, 2002; Toth, 1985). The evidence shows both a right-hand dominance in the construction of tools and an asymmetry in form of tools such that their use would be much more manageable with the right hand. Thus, the right bias in human handedness seems to be an evolutionary extension of a right bias in hominid handedness