Emotional contagion of distress in rats

Empathy is crucial for a successful social life. The discovery of mirror neurons has shed light on our understanding of human empathy as well as on one of its evolutionary predecessors, emotional contagion, in animals. This project aims to enrich our knowledge about emotional contagion, including an investigation of its underlying neural mechanism, an exploration of factors that modulate it, and an attempt to understand its function. The empirical endeavors throughout the project utilized a rat behavioral paradigm that models emotional contagion of distress. In this paradigm, an ‘observer’ rat witnesses a ‘demonstrator’ rat receiving painful stimuli such as electrical foot shocks or stimulations from a heat laser. Such manipulation typically results in the freezing of the demonstrator. Interestingly, the observer rat consistently freezes in response to the demonstrator. We use this socially triggered observer freezing (also called ‘vicarious freezing’) as a behavior index of emotional contagion of distress in rats and it has become the backbone of the project. The background, the rationale, and the goals of the research project are fleshed out in Chapter 1. The theoretical exposition chapter (Chapter 1) is followed by four chapters (Chapters 2-5) showing empirical evidence that substantiates the narrative of the dissertation recounted in the final chapter (Chapter 6).