Behaviour of domestic fowl in anticipation of positive and negative stimuli

Underlying the study of animal welfare is the assumption that animals experience emotional states. Although there has been a bias towards studying negative emotions, research into positive emotions is necessary for an overall welfare assessment. The aim of the current study was to find behavioural expressions specific for anticipation of different events in domestic fowl, Gallus gallus domesticus. To this aim, we used a Pavlovian conditioning paradigm by which we induced anticipation of a positive, neutral and negative event. We investigated whether birds were able to discriminate between sound cues signalling these events with different valences and, if so, whether anticipation of different events is reflected in different behavioural responses. The birds showed a response of increased attention to all sound cues. In anticipation of the negative event, the birds showed more head movements and locomotion than in anticipation of both the neutral and positive event, possibly reflecting the aversive nature of the negative event. In anticipation of the positive event, the birds showed more comfort behaviours, such as preening and wing flapping, which have been associated with a state of relaxation. Our study shows that laying hens are able to anticipate differentially a positive, neutral and negative event announced by different sound cues. It is also the first study to identify comfort behaviours as specifically associated with anticipation of a positive event in domestic fowl. Comfort behaviours may therefore be associated with a positive emotional state in domestic fowl.