Lundberg, P., Hartmann, E., Roth, L. S. V. 2020. Does training style affect the human-horse relationship? Asking the horse in a separation–reunion experiment with the owner and a stranger. Applied Animal Behaviour Science 233, 105144.
Humans have shared a long history with horses and today we mainly consider horses as companions for sports and leisure activities. Previously, the human perspective of the human-horse relationship has been investigated but there has been little focus on the horse’s perspective. This study aimed to reveal whether horses show attachment-related behaviour towards the owner compared to a stranger in a modified Strange Situation Procedure (SSP) consisting of a walking phase, a standing still phase, separation from the owner/stranger and lastly a reuinon. We tested 26 privately owned horses in an indoor experimental area of 20 × 14 m. In addition to testing, the owners were asked questions about their training methods. Based on these questionnaire results, owners were divided into groups depending on whether they mainly used negative reinforcement, positive reinforcement or a combination of both methods during training. They also completed a horse personality questionnaire. The results showed that the horses spent more time in door proximity when separated from the owner and the stranger (owner: Z = −3.46, P = 0.001; stranger: Z = 3.40, P = 0.001) compared to the reunion phase, and they sought human proximity during reunion. The horses’ heart rates were higher during the separation compared to the reunion with both the owner (Z = −3.44, P = 0.001) and the stranger (Z = −2.40, P = 0.016). These results are examples of attachment-related features and suggest that horses consider both the owner and the stranger as a safe haven. However, the results are not clear as to whether or not horses perceive their owners as a secure base since their exploratory behaviour during owner reunion was similar to that during stranger reunion. Interestingly, horses trained with positive reinforcement spent most time in door proximity during separation from the stranger (χ2(2) = 6.18, P = 0.045) and similarly there was a tendency also during owner separation (χ2(2) = 5.20, P = 0.074). The same group of horses also spent more time in stranger proximity (χ2(2) = 6.16, P = 0.046) and in physical contact with stranger (χ2(2) = 8.62, P = 0.013) than the other two training style groups during reunion. When correlating scores from the horse personality questionnaire with behaviours during owner reunion, we found few significant associations, but the trait Inquisitive correlated with both proximity to owner and ears forward (rs = 0.41, P = 0.035 and rs = 0.49, P = 0.011, respectively), and ears forward also correlated with the trait Excitability (rs = 0.39, P = 0.047) and Dominance (rs = 0.46, P = 0.019). Hence, this study revealed attachment-related behaviours of horses towards humans even though the results cannot resolve whether these fulfil all criteria for an attachment-bond.