The first paper with degus

Often we experience another individual’s perspective based on social cues without experiencing a specific event ourselves. For example, when we witness someone else undergo a frightening or painful ordeal, we may interpret their vocal or facial expressions such that we in turn become scared or hurt imagining how that person must be feeling. Transferring an emotional state from one person to another is known as emotional contagion, an elementary process of empathy that helps us form meaningful connections with each other.

What remains unclear is how social cues can influence neural phenomena in emotional contagion and its associated behaviours. Lidhar et al. sought to understand the social cues that allow for observational fear learning in degus, a highly vocal species of a communally living rodent that differ from many other rodents in their high degree of sociability and communication. The degus observed either a sibling or stranger receive foot-shocks in a distinct environmental context. The next day, the observer degus were placed in the shock context. During both parts of the process, the animals’ vocalizations and fear behaviours were measured.

Interestingly, degus who watched a sibling receiving foot-shocks demonstrated an enhanced fear response in the shock context, while those who initially watched a stranger did not. These results suggest social relationships may be a modulating factor on the degree of emotional contagion, specifically, that familiarity enhances emotional contagion while a lack of social relationship may hinder transfer. Additionally, analysis of vocalizations made by the degus during the experiments suggested a difference in fear responses of degus based on vocalization pattern but not number. Thus, vocalized expressions may also be an important social cue affecting emotional contagion.

Taken together, this evidence suggests that the social cues of familiarity and vocalization pattern play regulatory roles on the level of transferred fear in a degu who witnesses an unpleasant event without experiencing it themselves. This study provides a novel way of investigating study emotional contagion processes in animals while revealing the importance of vocal signalling and social relationships.

The study was led by a former postdoc, Dr. Nathan Insel (currently at University of Montana) and a former graduate student, Navdeep Lidhar (currently at University of Toronto Mississauga).