Posture and laterality in human and non-human primates: Asymmetries in maternal handling and the infant's early motor asymmetries

Abstract

This chapter is concerned with the question of the relations and possible influences of environmental factors on the establishment of patterns of manual lateralization in human and non-human primates. More specifically, we are interested in the relation between maternal postures and laterality in nonhuman primates (e.g. bias in cradling behaviour and hand preference of the mother) and the development of patterns of manual preferences in infants. In order to understand fully the many ways in which these variables could interact, we first review the evidence of postural biases in human adults when cradling and carrying their offspring. Next, we examine the divergent hypotheses advanced to explain the observed biases. The same is then done for non-human primates. A second part of our chapter (see Section 9.3) describes the different asymmetric patterns observed during the development of the infant concerning head turning, nipple preference, etc. i n both human and non-human primates.In a third part (see Section 9.4), we describe and compare the methods and definitions used by the different authors in their work. Then, we present the descriptions and definitions of behaviours that we are using in an ongoing study of Olive baboons (Papio anubis).Our main goal is to contribute to understanding the phylogenetic origins of hand laterality in humans by examining some of its possible determinants in non-human primates. Despite numerous efforts to propose models and explanatory schemata of hand laterality in non-human primates (e.g. MacNeilage, Studdert-Kennedy and Lindblom, 1987;Fagot and Vauclair, 1991; Ward and Hopkins, 1993), this question is still largely unresolved. On the other hand, views of determinants of hand laterality in humans still fluctuate between genetically (e.g. Annett, 1985Annett, , 1995 Hopkins and 307

Laterality in Maternal Cradling and Infant Positional Biases: Implications for the Development and Evolution of Hand Preferences in Nonhuman Primates

“…Several studies in humans showed that females have a left-sided cradling bias while males do not (Damerose and Vauclair, 2002). If we assume that a similar sex difference is evident in chimpanzees and gorillas, which would be difficult to determine because most males show little infant cradling, then whatever social or genetic factors selected for left-sided cradling was retained in human evolution as manifest in the extant sex differences seen in modern humans.…”

“…Several investigators have reported evidence of laterality in cradling biases in nonhuman primates, which are summarized in Table I (Damerose and Vauclair, 2002). It was not always clear whether a distinction was made by some authors between maternal cradling and infant positional biases (Table I).…”

“…Some authors have emphasized that environmental and experiential factors, such as interactions with parents and students, could influence the direction and the strength of manual laterality in humans (Provins, 1997); however, an explicit description of the role of cradling has not been suggested to explain the development of human hand preference despite considerable research on the topic of lateral bias in maternal infant cradling. Salk (1960) was the first to suggest that humans exhibit a left cradling bias for infants and the finding has been replicated in various human cultures (Damerose and Vauclair, 2002). Salk (1973) reported no association between maternal hand preference and maternal cradling bias, which may have led some to believe that the asymmetries in maternal cradling bias are due to biases related to expression of specific emotional states (Sieratzki and Woll, 1996).…”

Left Nipple Preferences in Infant Pan paniscus and P. troglodytes

“…laterality; mother-infant behavior; cradling; nipple preference Damerose and Vauclair (2002) and Hopkins (2004) recently suggested that early asymmetries in mother-infant behaviors may be the basis for the development of handedness. In particular, Hopkins (2004) argued that infant primates are not born into symmetrical environments but instead are exposed to imposed asymmetries by the caretaker, in the form of cradling biases, or the infants show explicit asymmetries in reflexive behaviors such as head orientation or limb strength (Fagot and Bard, 1995;Hopkins and Bard, 1995;Hopkins et al, 1997).…”

“…For example, humans, particularly women, show universal left-sided biases in cradling infants (Damerose and Vauclair, 2002). Researchers have reported a similar left-sided maternal cradling bias in great apes, notably in chimpanzees and gorillas, but not in other primates (Cunningham et al, 1989;Damerose and Vauclair, 2002;Dienske et al, 1995;Fischer et al, 1982;Hopkins, 2004;Lockard, 1984;Manning and Chamberlain, 1990;Manning et al, 1994;Rogers and Kaplan, 1995; Toback, 1999). Evidence of asymmetries in other early mother-infant behaviors of primates, such as nipple preferences, is less clear.…”