Expressions of emotions across species

Abstract

What are emotions and how should we study them? These questions give rise to ongoing controversy amongst scientists in the fields of neuroscience, psychology and philosophy, and have resulted in different views on emotions [1-6]. In this review, we define emotions as functional states that bear essential roles in promoting survival and thus have emerged through evolution. Emotions trigger behavioral, somatic, hormonal, and neurochemical reactions, referred to as expressions of emotion. We discuss recent studies on emotion expression across species and highlight emerging common principles. We argue that detailed and multidimensional analyses of emotion expressions are key to develop biology-based definitions of emotions and to reveal their neuronal underpinnings.

Figure 1

Modes of emotion expression. Emotions are expressed through several modalities summarised in this schematic. Across species (inner circle) organismal response to a relevant stimulus can evoke changes in locomotion, motor behaviour, facial expressions, vocalisations, cardiovascular, gut and endocrine reactions and arousal (outer circle). Emotions, together with their expressions, have been proposed to encompass different features (middle circle) which are explained in further detail in Box 1.

Figure 2

Functional roles of emotion expression. Expression of emotion across species has been shown to support: self-centered, social and communication as well as instructive and feedback functions.