Asymmetries in the visual processing of emotional cues during agonistic interactions by gelada baboons.

Orientational asymmetries of male gelada baboons were assessed to determine visual field preferences during agonistic and post-conflict behaviour using photographic sequences of aggressive interactions and records of facial injuries. Both opponents used their left visual field significantly more frequently than their right during fights, threats and approaches; the degree of left visual field preference varied with the level of negative emotion. During post-conflict behaviour, only the non-retreating animal showed a significant left visual field preference. The observed left visual field preferences appear to indicate a right hemisphere dominance in the processing of emotional information. Other possible causes of the baboons' observed visual field preference (including processing of auditory cues and visuospatial information, lateralised control of the brain over facial expression, and the asymmetrical signalling capacity of the face) are discussed.