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

Abstract

Left-sided maternal cradling has been widely reported in human populations. In this paper, I review the evidence of laterality in maternal cradling and infant positional biases in non-human primates. The review revealed some evidence of population-left sided cradling in great apes but little consistency in bias was found among Old and New World monkeys. Very little data have been reported in prosimians. I further describe how asymmetries in either maternal cradling or infant positional biases may explain individual and species differences in hand preference.

Fig. 1

Mean HI for offspring handedness for simple reaching and female cradling biases in a sample of 15 chimpanzees. HI = handedness index and is derived following the formula HI = (#R−#L)/(#R+#L). Positive values reflect right-hand biases and negative values left-hand biases.

Fig. 2

Mean absolute HI scores for cradling bias in primiparous and multiparous females. Mean absolute HI scores for reaching in offspring born to primiparous and multiparous females.

Fig. 3

Concordance in hand preference in full and maternal half-sibling chimpanzees for two separate measures of hand use including bimanual feeding and the TUBE task (Hopkins, 1994, 1995b).

Fig. 4

Mean cradling and handedness scores for 6 different primate species tested on the TUBE task.