Embracing your emotions: affective state impacts lateralisation of human embraces.

Humans are highly social animals that show a wide variety of verbal and non-verbal behaviours to communicate social intent. One of the most frequently used non-verbal social behaviours is embracing, commonly used as an expression of love and affection. However, it can also occur in a large variety of social situations entailing negative (fear or sadness) or neutral emotionality (formal greetings). Embracing is also experienced from birth onwards in mother-infant interactions and is thus accompanying human social interaction across the whole lifespan. Despite the importance of embraces for human social interactions, their underlying neurophysiology is unknown. Here, we demonstrated in a well-powered sample of more than 2500 adults that humans show a significant rightward bias during embracing. Additionally, we showed that this general motor preference is strongly modulated by emotional contexts: the induction of positive or negative affect shifted the rightward bias significantly to the left, indicating a stronger involvement of right-hemispheric neural networks during emotional embraces. In a second laboratory study, we were able to replicate both of these findings and furthermore demonstrated that the motor preferences during embracing correlate with handedness. Our studies therefore not only show that embracing is controlled by an interaction of motor and affective networks, they also demonstrate that emotional factors seem to activate right-hemispheric systems in valence-invariant ways.