Horses are genetically pre-programmed to react to horse actions in a specific manner.
When one performs the actions of a lead horse, horses react accordingly. Now that is what it all boils down to. One acquires it by scrupulously observing how horses act with each other when there is no human influence to alter the interaction. Since there is no good or bad in nature, one cannot put emotional assessments to the actions. One must realize that these actions are for the ulimate good of the individual by preserving harmony within the group.