Walruses, Bats, and Humans Cuddle Their Young to Help The Brain Develop

Humans and other primate-like animals all share numerous behavioral characteristics, including the means in which they mother their offspring. One commonality shared by these species is their conscious choice to lateralize their feeding and positioning behaviors to their offspring. Specifically, mothers seem to prefer to hold their offspring on their left side while feeding as well as ensuring that their young are looking at them using their left peripheral vision. This idea of behavioral lateralization is predicted to have numerous distinct advantages, including improved cognitive and motor abilities, increased escape ability, and a strong social intelligence. Particularly, when mothers use their left side to nurture an infant, the infant will respond by activating their right cortex; the brain region responsible for recognition of external stimuli, including emotions and social cues. For decades it was thought that humans and other primate like mammals were the only species to adopt the left-right bias with their young, however a new study has revealed that Pacific Walruses and Indian Flying Foxes also demonstrate this behavior. In this study, researchers analyzed key interactions between mother walruses and flying foxes with their offspring in order to identify if either generation showed a lateral bias. What they were able to identify, was that mother walruses predominantly chose to hold their offspring face to face and on their left side, ensuring that their left eye was in constant view of the infants left side. Interestingly, when infant walruses were floating by their mothers, they also chose to maintain a left sided field of vision with their mothers. This lateralization was identical to what researches saw when observing the Flying Foxes. Although upside down, the mother and child flying foxes also maintained a left sided viewpoint during face to face resting as well as during suckling. Taken together, the results from this analysis indicate that both mother and child make conscious decisions to maintain left-right lateralization. On a larger scale, the results also show that the left sided positional bias is not specific for primate like species, but could be a common feature of numerous species of mammals. This suggests that left sided bias not only enhances social processing, but is a strong evolutionary advantage for iteroparous species.

Reference

• Andrey Giljov et al. Facing each other: mammal mothers and infants prefer the position favouring right hemisphere processing, Biology Letters (2018).

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