As humans we know that that it can be reassuring to have someone by our side in challenging situations. We assume that other social species benefit from this effect, known as social support, too. Our study aimed to investigate the effect of social support on pigs trained and tested on a Judgement Bias Task (JBT), a task designed to determine if an animal is rather optimistically or pessimistically minded. Studying animals’ responses in such a task helps us to understand how they perceive their environment and what they feel in different situations. In a JBT, animals are usually trained and tested in social isolation to make data collection more convenient and to avoid distraction potentially caused by other individuals. However, science suggests that social isolation can be a stressor itself, which seems quite counterintuitive when we want to assess animals’ emotions.

This is why we compared piglets trained and tested in social isolation with piglets going through the same procedure, but with social support, i.e. companion animals on their side, with whom they could have visual and physical contact during training and testing. Piglets did not differ regarding learning speed or the test results as both groups responded similarly optimistic/pessimistic in the task. However, isolated pigs showed more fear-related behaviour, e.g. squealing and escape attempts. Our findings suggest to consider using companion animals in behavioural tests to enhance pig welfare in research, but further research is required gain a deeper understanding of the advantages of social support and how to best use social companion animals in research with pigs and potentially other social species.