Laterality of cradling in relation to perception and expression of facial affect.

A dominant leftward cradling bias has been observed in women in non feeding interaction with infants. Reasons for this behavior have been sought in behavioral asymmetries, but none have sufficiently justified the presence of this leftward pattern. Recently, the cradling bias has been linked to affective processing, considered to be a specialized function of the nondominant (right) hemisphere (Manning & Chamberlain, 1990). This study investigates Manning and Chamberlain's (1990) suggestions that a relationship exists between leftward cradling and the interpretation and expression of affect. Eighty-six nulliparous women were tested for this relationship by correlating direction of cradling bias with visual field dominance for perception of facially expressed emotion and expression of affect. No significant relationship was found to directly support the hypotheses.

Lateral asymmetry and tactile sensitivity.

Weinstein found in 1963 that the left female breast is more sensitive to tactile stimulation than the right breast. Saling and Cooke in 1984 hypothesized that this asymmetry in breast sensitivity underlies the well-documented leftward bias in maternal cradling behaviour, which is independent of manual specialization. Our interest in the Saling and Cooke hypothesis led to an attempt to replicate Weinstein's 1963 study. His findings were not supported. Further, a review of the literature on the lateral distribution of cutaneous thresholds showed that there is little experimental support for the widely held belief that the left side of the body is uniformly more sensitive than the right.