Happiness takes you right: the effect of emotional stimuli on line bisection

Emotion recognition is mediated by a complex network of cortical and subcortical areas, with the two hemispheres likely being differently involved in processing positive and negative emotions. As results on valence-dependent hemispheric specialisation are quite inconsistent, we carried out three experiments with emotional stimuli with a task being sensitive to measure specific hemispheric processing. Participants were required to bisect visual lines that were delimited by emotional face flankers, or to haptically bisect rods while concurrently listening to emotional vocal expressions. We found that prolonged (but not transient) exposition to concurrent happy stimuli significantly shifted the bisection bias to the right compared to both sad and neutral stimuli, indexing a greater involvement of the left hemisphere in processing of positively connoted stimuli. No differences between sad and neutral stimuli were observed across the experiments. In sum, our data provide consistent evidence in favour of a greater involvement of the left hemisphere in processing positive emotions and suggest that (prolonged) exposure to stimuli expressing happiness significantly affects allocation of (spatial) attentional resources, regardless of the sensory (visual/auditory) modality in which the emotion is perceived and space is explored (visual/haptic).