The IntricateWeb of Asymmetric Processing of Social Stimuli in Humans

Although the population-level preference for the use of the right hand is the clearest example of behavioral lateralization, it represents only the best-known instance of a variety of functional asymmetries observable in humans. What is interesting, is that many of such asymmetries emerge during the processing of social stimuli, as often occurs in the case of human bodies, faces and voices. In the present paper, after re-viewing previous literature about human functional asymmetries for social and emo-tional stimuli, we suggest some possible links among them and stress the necessity of a comprehensive account (in both ontogenetic and phylogenetic terms) for these not yet fully explained phenomena. In particular, we propose that the advantages of laterali-zation for emotion processing should be considered in light of previous suggestions that (i) functional hemispheric specialization enhances cognitive capacity and effi-ciency, and (ii) the alignment (at the population level) of the direction of behavioral asymmetries emerges, under social pressures, as an evolutionary stable strategy.