Lateral Asymmetries in Behaviour in Neonates

A Thesis submitted to the University of Manchester for the degree of M.Sc. in the Faculty of Medicine,
Department of Child Health

As part of the initial phase of a prospective study of the development of laterality, one hundred and fifty babies were tested in the neonatal period for the existence of lateral asymmetries in behavior. Palmar and plantar grasp response and head-turning behavior were tested on two consecutive days. As many babies held an object longer in their left hand as held longer with the right. Head turning, however, was markedly asymmetrical, with 52% of the babies turning predominantly to the right and only 16% turning predominantly to the left. The possible relationship of the direction of head-turning to obstetrical and other environmental factors was examined.

No relationship was found between such obstetrical factors as birth position, birth order and time to establish regular respirations although a slightly higher proportion of babies who turned predominantly to the left were born from an LOA rather than an ROA birth position.

Some interesting maternal asymmetric behavior was found. Most mothers preferred to hold their infants to the left and more mothers laid their babies down on their right sides. The right-lying position correlated significantly with head-turning preference in that babies who were laid on their right sides were more likely to turn to their right.
These results were compared with the findings of others and their implications discussed.

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