Communication, Emotional Contagion and post-conflict third party interaction in geladas (Theropithecus gelada)

Abstract

In literature, empathy has been characterized by a disagreement regarding the exact nature of the phenomenon. There are emotional, cognitive, and conditioning views of empathy, and these views apply to different extents across species. These forms of emotional linkage support group alarm, vicariousness of emotions, mother-infant responsiveness, and the modelling of competitors and predators; these forms have profound effects on reproductive success. Taking into account the possible mechanisms underlying gelada’s spontaneous yawn, emotional contagion and emotional response to conflicts between other group members, our results provide information which can have important theoretical implications. In fact, our findings are consistent with the view that contagious yawning reveals an emotional connection between individuals and also that empathy could be one of the mechanisms involved in triadic post-conflict affiliation. We recorded the behaviours of individual belonging to two colonies of geladas, (Theropithecus gelada), a species characterized by a female-centred one-male society, living at the NaturZoo (Rheine, Germany). Data were collected during a 6-month period in 2007 (June-November), a 4-month period in 2009 (June-September), a 2-month period in 2010 (July-August) and a 2-month period in 2011 (July-August). The gelada is a good model species because they have a strong sexual dimorphism, a clear-cut linear hierarchy, high social cohesiveness and fine-tuning towards companions. In the first study, we focussed on some social hypotheses on the potential functions of spontaneous yawning according to its patterns and contexts. Geladas, perform yawning according to three different visual intensity modalities, which are easy to be detected due to the diverse degree of mouth opening. We investigated whether the patterns of the yawn performance is predictive of its potential functions. YW1, YW2, and YW3 can transmit different meanings according to the performer, the context and the behavioural pattern temporally associated to the yawn event. Moreover scratching, used as a reliable measure of anxiety, increased after each yawning type, even though the subjects tended to scratch themselves more after YW3, thus suggesting that this type of yawn can indicate an even higher variation of arousal. All the three types of yawning were more frequent in the early morning with YW3 also showing an additional daily peak (pre-feeding). Even though a clear cut functional distinction of the diverse types of gelada yawns is complicated, we suggest that YW1 and YW2, being more linked to an emotional internal state, can be considered "true" yawns and YW3 can function as a multimodal signal which can be more modulated and affected by external social events. In the second study we assessed that in gelada baboons yawning is contagious, especially between socially close individuals; in fact, the contagiousness of yawning correlated with the level of grooming between subjects. Adult females showed precise matching of different yawning types, which suggests a mirroring mechanism that activates shared representations. We suggested that females have an enhanced sensitivity and emotional tuning toward companions compared to males. In the third study, we tested some hypotheses on the potential functions of triadic affiliation in geladas. We enlightened that the positive outcome of the triadic post-conflict affiliation is focussed more on victims than on bystanders (Self-Protection Hypothesis) or other group members (Tension Reduction Hypothesis), which apparently do not gain any kind of benefits by the behaviour. Moreover, it seems that triadic post-conflict affiliation does not have a role in restoring relationships between former opponents (Substitute for Reconciliation Hypothesis), so that reconciliation and triadic post-conflict affiliation co-exist and co-cooperate for two different purposes. After conflicts of high intensity levels, triadic affiliation improves the emotional state of the victim (Consolation Hypothesis) by lowering his/her levels of anxiety, especially when the victim is a kin or a close-bonded partner. In this case, a stronger emotional response can be elicited in the third-party which directs a higher frequency of affinitive acts towards the victim as predicted by the sympathetic concern hypothesis already suggested for humans and apes. As a whole, our findings indicate that two of the multiple levels of empathy described in literature for humans and apes (emotional contagion and sympathetic concern) are probably present in monkeys as well.