Developmental cascades as a framework for primate handedness

Abstract

November CITATION Nelson EL () Developmental cascades as a framework for primate handedness.

Environmental and genetic determinants of sensorimotor asymmetries in mother-infant interaction

“…It is plausible that lateralized cradling interactions might be part of a complex system involving several genetic and epigenetic mechanisms. It should be pointed out that, in line with this view, many ethological studies (mainly in avian species; e.g., Rogers, 1982 , 1997 ) have shown interesting links between the exposure to lateralized environmental stimuli during the early stages of development and the later establishment of hemispheric asymmetries, which seem to entail the related appearance of specific behaviors (Nelson, 2022 ). In light of the literature reviewed above, we believe that the investigation of further possible effects of typical and atypical cradling on infant cognitive and affective development is warranted.…”

Handedness as a major determinant of lateral bias in human functional cradling

“…Why a person develops a distinct preference for one hand or foot over the other has not been fully accounted for, but rather than posing that handedness is shaped by genetic or environmental factors, or a combination thereof, more and more scholars argue that handedness emerges as the result of developmental cascades beginning prenatally (e.g., Campbell et al., 2018; Michel et al., 2013). For example, Nelson (2022) describes a postural asymmetry in the intrauterine environment as the result of fetal growth so that the more the fetus grows, the more restricted its position and movements become. In preparation for birth, the fetus turns head‐down with the head turned such that one ear (typically the right) faces outward.…”

“…In preparation for birth, the fetus turns head‐down with the head turned such that one ear (typically the right) faces outward. In this position, movement of the left arm of the fetus is restricted more than that of the right arm (Nelson, 2022). This prenatal asymmetry has been put forward to underlie handedness in humans (Previc, 1991).…”

“…This, in turn, predicts their later hand preference for manipulating objects (Babik & Michel, 2016; Campbell et al., 2015). Taken together, there is now ample evidence that handedness emerges in human infants via cascading developmental events (Nelson, 2022). The developmental cascades' perspective (e.g., Iverson, 2021; Masten & Cicchetti, 2010) offers a new framework to understand change that focuses on how change is the result of a multitude of factors across a range of levels and systems.…”

“…Humans prefer to use their non‐dominant hand for cradling young infants, and as the ratio between right‐handers and left‐handers is estimated to be 9:1 (Corballis, 2003), there is a considerable majority of right‐handers in the population who consequently cradle in their non‐dominant left arm. Rather than introducing a genetic hemispheric asymmetry in emotional processing that is assumed stronger in women than men (e.g., Vauclair, 2022), a much more elegant explanation is that handedness emerges in human infants via cascading developmental events starting already in the intrauterine environment (Nelson, 2022), and that women and girls have more experience with handling babies and dolls. As a result, they are learning‐by‐doing from an early age that cradling in the non‐dominant arm is more practical because it leaves the dominant hand free for doing other things with.…”