The contribution of postural bias to lateral preferences for holding human infants

When asked to hold an infant, 60-85% of adults hold on their left, so that the infant's head is to the left of their midline (Brüser, 1981; de Chateau, 1983; Saling & Tyson, 1981). The same group bias has been found even when persons are merely asked to imagine holding an infant (Nakamichi & Takeda, 1995; Harris, Almerigi, & Kirsch, 2000). A number of variables have been found to contribute modestly to the bias, including the sex and handedness of the holder. In the current study, the role of a new variable is investigated, namely, the feeling of comfort for holding an infant on a particular side as indexed by one's foot preference for acts of stabilizing or postural support. To test this hypothesis, 282 right-handed college students (218 women, 64 men) were given the imagine-hold task along with 4 questions about their foot preference for posture and balance. The results showed that, at least for women, the two measures were modestly but significantly related.