Repeated Witnessing of Conspecifics in Pain: Effects on Emotional Contagion

Abstract

Witnessing of conspecifics in pain has been shown to elicit socially triggered freezing in rodents. It is unknown how robust this response is to repeated exposure to a cage-mate experiencing painful stimulation. To address this question, shock-experienced Observer rats repeatedly witnessed familiar Demonstrators receive painful footshocks (six sessions). Results confirm that Observers freeze during the first testing session. The occurrence of this behaviour however gradually diminished as the experimental sessions progressed, reaching minimal freezing levels by the end of the experiments. In contrast, the appearance and continuous increase in the frequency of yawning, a behavior that was inhibited by metyrapone (i.e,. a glucocorticoid synthesis blocker), might represent an alternative coping strategy, suggesting that the observer’s reduced freezing does not necessarily indicate a disappearance in the affective response to the Demonstrator’s distress.

The roots of empathy: Through the lens of rodent models

“…Though generally appearing in non-fearful situations, yawning has been also observed in stressful situations in different species and can serve as a possible indicator of increased stress (Aureli and de Waal, 1997; Kubota et al, 2014; Leone et al, 2014; Miller et al, 2012). In line with this hypothesis, a reduction of yawning has been observed following administration of the glucocorticoid synthesis blocker, metyrapone (Carrillo et al, 2015). However, intranasal oxytocin, believed to suppress stress and enhance empathy (Hurlemann et al, 2010), did not affect yawning per se , but increased awareness of the act in participants, which resulted in higher rate of efforts made to conceal it (Gallup and Church, 2015).…”

“…Magnitude of vicarious freezing response was modulated by previous experience with shocks (Atsak et al, 2011; Sanders et al, 2013), familiarity (Jeon et al, 2010; Gonzalez-Liencres et al, 2014), genetic background (Chen et al, 2009), and rearing conditions (Yusufishaq and Rosenkranz, 2013; Panksepp and Lahvis, 2016). Interestingly, repeated exposure to a cage mate experiencing foot shocks resulted in a gradual decrease of socially triggered freezing in the observers (Carrillo et al, 2015). It is noteworthy that vicarious fear learning is associated trait measure of empathy in humans (Kleberg et al, 2015), which indicates that the rodent models described above may tap into some fundamental features of empathy across species.…”

Understanding others: Emotion recognition in humans and other animals

“…Most rodents are social animals, living substantial parts of their lives in groups of variable size and displaying a rich repertoire of social behaviors. Similar to humans and to the other animal species described above, rodents have been recently shown to be able to perceive and react to the emotional state of conspecifics, and in some cases, to produce complex pro‐social behaviors possibly related to empathy . However, research on rodent emotion recognition in settings similar to the ones described above is still underdeveloped.…”

Behavioral and mechanistic insight into rodent empathy

“…Conversely, an increased stress response has been found to underlie distress in social observational learning. The repeated witnessing of a conspecific in pain triggers freezing responses in rats, a behavior that eventually decreases and is replaced by spontaneous yawning (Carrillo et al, 2015). In this context, yawning is hypothesized to reflect increased distress and a coping strategy.…”

“…Yawn contagion has been reported to occur in a variety of species including humans, bonobos, chimpanzees, parrots, and dogs (Demuru and Palagi, 2012;Massen et al, 2012;Miller et al, 2012;Romero et al, 2013) and susceptibility to contagious yawning is correlated with social familiarity (Demuru and Palagi, 2012;Romero et al, 2013). Interestingly, rats are known to yawn and in some situations yawning is considered a sign of distress (Carrillo et al, 2015). The neuropeptide oxytocin, known for its role in social communication and bonding (Bartz et al, 2010;Rodrigues et al, 2009b) has been shown to induce yawning in male rats (Sanna et al, 2012).…”