Facial expressions and emotions in domestic animals.

Abstract

Abstract In many animal species, facial expressions are key elements for recognizing emotions and numerous types of social interaction. Emotions are complex reactions that allow individuals to cope with full events that have either positive or negative meaning and involve certain neurophysiological responses proper to each emotion and species. Regulation of emotional states requires integrating a whole series of responses - peripheral, autonomous, endocrine and muscular - that entail activating various sub-cortical structures, including the amygdale, hypothalamus and brainstem. In recent decades, interest in the emotions expressed by animals has grown, and researchers have come to understand that some problems of animal welfare can be detected by examining and comprehending the emotional experiences that animals may suffer, and identifying how they demonstrate their reactions through facial expressions and corporal postures. The objective of this review is to examine recent literature on aspects related to the function of the emotions and facial expressions in certain domestic species (cats, dogs, rats, sheep, horses and pigs) and propose that understanding facial expressions can be useful as a complement to existing tools in assessing welfare and working with, or doing research on, these species.