Emotion: intense but short-lived affective response to an event, which is associated with specific body changes […] that gave the animals the ability to avoid harm/punishment or to seek valuable resources/reward (Boissy et al., 2007). 

Boissy, A., Manteuffel, G., Jensen, M. B., Moe, R. O., Spruijt, B., Keeling, L. J., Winckler, C., Forkman, B., Dimitrov, I., Langbein, J., Bakken, M., Veissier, I., & Aubert, A. (2007). Assessment of positive emotions in animals to improve their welfare. Physiology & Behavior, 92(3), 375–397. https://doi.org/10.1016/j.physbeh.2007.02.003