Abstract
Simple SummaryThe aim of the current study was to investigate the side (left or right) and sagittal preference (front or rear) of adult Barbary macaques (Macaca sylvanus) during different types of social interactions. This study would improve our knowledge of the implication of emotions, through the investigation of behavioral lateralization, during social interactions and communication in macaques. No side preferences were found for any social interaction, suggesting that both hemispheres might be complemental and balance each other during intraspecific communication. For the sagittal preference, we found that macaques are kept in front rather than on the rear by close conspecifics, presumably due to the need to detect emotions and intentions of conspecifics during social interactions.Social laterality in non-human primates has started to attract attention in recent years. The positioning of individuals during social interactions could possibly suggest the nature of a relationship and the social ranking of the subjects involved. The subjects of the present study were 12 adult Barbary macaques (Macaca sylvanus) housed in a zoological garden. We carried out fourteen 210-min video-recorded sessions and we used a focal animal sampling method to collect the position of the subjects during different social interactions. Data on the position of each macaque during three types of social interactions were collected (approach, proximity and affiliative contacts). Moreover, we focused on the outcomes of dyadic agonistic encounters to build the hierarchy of the colony. For each social interaction, two conditions were considered: the side preference (being kept on the left or on the right) and the sagittal preference (being kept in front or on the rear). Bouts of preference of different positions were collected for different social interactions (approach, proximity and contacts). No group-level side preferences were found for any social interaction, suggesting that both hemispheres might be complemental and balance each other during intraspecific communication. For the sagittal preference, we found a group-level bias for proximity, with macaques being kept in front rather than on the rear by close conspecifics. This might be due to the need to detect emotions and intentions of conspecifics. Moreover, high-ranking individuals are kept more frontally than on the rear when in proximity with other macaques. More studies are needed to better investigate social laterality, possibly distinguishing more categories of social interaction, and detecting other variables that might influence the positioning preferences.
Highlights
Hemispheric specialization is intended as the division of roles between the two cerebral hemispheres, with the left side of the brain involved for example in the process of routine actions whereas the right side deals with spatial cues of the environment and unexpected stimuli, and in some contexts has been suggested to control social stimuli [1].choosing to use one side of the body or the other could be convenient in certain situations as it would facilitate behaviors under the control of a specific hemisphere [2,3,4].Non-human primates living in complex social groups and showing a large repertoire of social activities can be an ideal model to study laterality of social behaviors, and its evolutionary emergence in humans
The ANOVA between different social interactions revealed no significant differences in the Side Index (SI) (F(2) = 0.03; p = 0.970) (Figure 2A), whereas we reported a significant difference considering the ABS-SI (F(2) = 5.19; p = 0.011); Tukey HSD
The ANOVA between different social interactions revealed no significant differences in the SI (F(2) = 0.03; p = 0.970) (Figure 2A), whereas we reported a significant difference considering the ABS-SI (F(2) = 5.19; p = 0.011); Tukey HSD post hoc tests revealed that the ABS-SI for affiliative contacts were significantly higher than the ABS-SI for approach and for proximity (Figure 2B)
Summary
Hemispheric specialization is intended as the division of roles between the two cerebral hemispheres, with the left side of the brain involved for example in the process of routine actions whereas the right side deals with spatial cues of the environment and unexpected stimuli, and in some contexts has been suggested to control social stimuli [1].choosing to use one side of the body or the other could be convenient in certain situations as it would facilitate behaviors under the control of a specific hemisphere [2,3,4].Non-human primates living in complex social groups and showing a large repertoire of social activities can be an ideal model to study laterality of social behaviors, and its evolutionary emergence in humans. The behavioral responses to social stimuli have been found to be lateralized in several taxa, with each hemisphere dealing with recognition of individuals (in terms of identification and social rank), interpretation of facial expressions and management of affiliative and agonistic interactions [3,5]. In non-human primates, asymmetries in the display of facial expressions have been reported in different species, with the left side of the face producing facial expression earlier and more intensively than the right side in monkeys [13,14,15] and great apes [16]. In wild chimpanzees the nature of social relationships influenced laterality, with a prevalence of right-handed gestures in context requiring efficient communication [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
