Social Facilitation (or social learning): the behaviour of a conspecific changes the motivation of another conspecific observing it, resulting in the tendency of animals to do what other individuals are doing (from Rørvang et al., 2018). 

Rørvang M. V., Christensen, J. W., Ladewig, J., & McLean, A. (2018). Social Learning in Horses—Fact or Fiction? Frontiers in Veterinary Science, 5, 1–8. https://doi.org/10.3389%2Ffvets.2018.00212