Contagious yawning in gelada baboons as a possible expression of empathy

Abstract

Yawn contagion in humans has been proposed to be related to our capacity for empathy. It is presently unclear whether this capacity is uniquely human or shared with other primates, especially monkeys. Here, we show that in gelada baboons (Theropithecus gelada) yawning is contagious between individuals, especially those that are socially close, i.e., the contagiousness of yawning correlated with the level of grooming contact between individuals. This correlation persisted after controlling for the effect of spatial association. Thus, emotional proximity rather than spatial proximity best predicts yawn contagion. Adult females showed precise matching of different yawning types, which suggests a mirroring mechanism that activates shared representations. The present study also suggests that females have an enhanced sensitivity and emotional tuning toward companions. These findings are consistent with the view that contagious yawning reveals an emotional connection between individuals. This phenomenon, here demonstrated in monkeys, could be a building block for full-blown empathy.

Fig. 1.

Three different yawning displays performed by geladas. (A) A CT yawning. (B) An UT-yawning. (C) An UG-yawning.

Fig. 2.

Frequency of yawning. (A) Frequency of yawning performed in the presence and absence of the visual stimulus is shown. We considered only nonvocalized yawning as stimulus; however, we cannot exclude the influence of audible respiratory movements. (B) Frequency of yawning performed in the presence and absence of the acoustic stimulus (vocalized yawning) is shown. In this case the receiver was not able to see the first yawner so the visual cue can be excluded.

Fig. 3.

Frequency of contagion distribution as a function of the minutes of observation is shown.

Fig. 4.

Matching response. (A) Type of yawning response as a function of type of previous yawning when the first yawner (stimulus) was a female is shown. A matching response is present only for CT and UT. (B) Type of yawning response as a function of type of previous yawning when the first yawner (stimulus) was a male is shown. There is no matching response for any of the three types of yawning.

Fig. 5.

Grooming and contagion. The scatter-plot shows the correlation between the frequency of grooming interchange (y axis) and the level of contagion (x axis).