Why people have lateral preferences when kissing and hugging

Typically, a person will initiate a hug with the right hand. Similar preferences are also present in other forms of social touch. The question of handedness plays a role in the process. However, it is not the only relevant aspect.

When touching others in a social context, for example, kissing or hugging, people often have a lateral preference; they will, for example, tend to tilt their head to the right rather than to the left when kissing. There are many theories as to the causes. In a review article published in the journal Neuroscience & Biobehavioral Reviews, researchers from Ruhr-Universität Bochum, Heinrich-Heine-Universität Düsseldorf and Victoria University of Wellington have analyzed existing data to verify the theories. The article was published online in October 2018.

The team headed by Associate Professor Sebastian Ocklenburg and Julian Packheiser from the Department of Biopsychology in Bochum has concluded that the observed results cannot be explained solely by right or left-handedness. Handedness does play a role, but so does the emotional context.

Left shift in emotional situations

"In general, the population at large has a preference of tilting the head to the right when kissing, to initiate a hug with the right hand, and to cradle a baby in the left arm," says Julian Packheiser. With regard to kissing and hugging, the assumption is that people have a dominant hand that they use to initiate the motion. According to the theory, the dominant hand is kept unoccupied when cradling a child so that it can be used to perform other tasks.

"As social touches are often associated with a hand motion, it is an obvious assumption to make that the handedness affects lateral preferences," says Sebastian Ocklenburg. In their review article, the researchers have listed numerous studies that substantiate the influence of handedness. However, that alone cannot explain the lateral preferences; the emotional context, too, is relevant.

"In emotional situations, the lateral preference shifts to the right," describes Packheiser. "It doesn't matter if the emotions are positive or negative." As far as the preference is concerned, it is irrelevant if two people hug because they are happy to see each other, or because one is comforting the other.

Emotions are processed asymmetrically in the brain

The researchers explain the left shift in emotional—as opposed to neutral—situations by speculating that emotions are primarily processed in the right brain hemisphere, which is responsible for movements of the left side of the body. "There is ample evidence of interaction and interconnection of motor networks and emotional networks in the brain," points out Ocklenburg. The theory of right-hemispheric processing of emotions is backed by behavioural data from studies on social touch as well as by results gained in imaging and neurophysiological studies.

According to the authors, the asymmetry present in human social touch can be best explained by a combination of motor preferences and right-hemispheric emotional dominance.