Onur Guentuerkuen, Nature 421, 711 (13 Feb 2003): Adult peristence of head-turning asymmetry. A preference in humans for turning the head to the right, rather than to the left, during the final weeks of gestation and for the first six months after birth constitutes one of the earliest examples of behavioural asymmetry and is thought to influence the subsequent development of perceptual and motor preferences by increasing visual orientation to the right side. Interestingly, twice as many adults turn their heads to the right as to the left when kissing, indicating that this head-motor bias persists into adulthood. Of 124 kissing pairs, 80 (64.5%) turned their heads to the right and 44 (35.5%) turned to the left (ratio ~ 2:1), which is statistically significantly different from 50% (1:1). Funny, what some people do research on!