On your terms or mine: pigs' response to imposed gentle tactile contact vs. free form interaction with a familiar human.

Positive human-animal interactions (HAIs) can be intrinsically rewarding and facilitate positive human-animal relationships. However, HAI paradigms vary across studies, and the influence of different interaction paradigms on the animal's response has been overlooked. We compared the behavioural responses of pigs (n = 28) individually tested with two types of gentle tactile interactions with a familiar human: 'free form (FF)' where the pig could voluntarily approach and interact as they normally would, and 'imposed contact (IC)' where the human imposed tactile contact on the pig according to a standardised protocol. Pigs did not differ in their level of engagement with the human between the two types of interactions. However, they differed in their behaviour as they explored the pen more during the FF test, while they emitted more low-pitched vocalisations (grunts) during the IC test. These differences can likely be imputed to the IC test differing to the pigs' habituation to human contact, which could have evoked greater attention to the human or triggered frustration due to violation of expectation. These findings highlight the influence of the predictability of the interaction or level of agency provided to the animal in HAI tests and relation to their previous experience of interacting.