Vocal expression of emotions in pigs during anticipation of positive social contexts: Impact of human animal relationship
2019
Villain, Avelyne | Hazard, Azelie | Guérin, Carole | Boissy, Alain | Tallet, Céline
‘Emotions’ have long been considered as a human specificity. We now know that animals have emotional states characterised by their valence and arousal. Vocal signals carry emotional information and they provide a way to assess the origin and evolution of emotions. We thus studied vocal expression of emotions in domestic pigs, which use several call types in various contexts and are known to be able to anticipate events. We chose to focus on anticipation, which is supposed to trigger more intense emotions than the situations itself. Using a two-way associative learning assay, 60 pigs were trained to learn to anticipate a reunion with either their conspecifics (positive event) or a human. Half of the pigs were habituated to human repetitive positive interactions and were expected to form a positive relationship with the caretaker. The other half were expected to express fear of the caretaker and then get used to this neutral event. This paradigm allowed us to assess how pigs do express anticipatory emotions differing in their valence and arousal. Behaviours, heart rate and vocal expression were monitored. By decoding vocal flexibility in pigs, we provide perspectives for assessing positive emotions in pigs, which may have application to assessing pig welfare.
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