Emotional experience in sheep: Predictability of a sudden event lowers subsequent emotional responses

The study of emotions in animals can be approached thanks to a framework derived from appraisal theories developed in cognitive psychology, according to which emotions are triggered when the individual evaluates challenging events. This evaluation is based on a limited number of criteria such as the familiarity and the predictability of an event. If animals are able to experience emotions rather than simply displaying reflex responses to their environment, then their appraisal of events should, as in humans, modulate their emotional responses. We tested this hypothesis by comparing vocalisations, feeding behaviour, and the startle and cardiac responses of lambs submitted to a sudden event that could or could not be predicted. Lambs able to predict the sudden event thanks to a light cue (associative predictability) showed weaker suddenness-induced startle and cardiac responses and spent more time feeding than their counterparts, thus supporting the existence of an emotional experience in these animals. Furthermore, lambs submitted to the regular appearance of the sudden event (temporal regularity) vocalised less and left less unconsumed food deliveries than lambs submitted to random appearances of the sudden event (controls). These results underline that the cognitive abilities of animals should be taken into account when assessing their emotional experiences and more generally their mood states, which are underlying factors of animal welfare. (C) 2007 Elsevier Inc. All rights reserved.