The convention of leading and mounting the horse from the left might be more than just tradition, according to a new study from St. Andrews University. The study, led by Kate Farmer, MA, at the Harmony Center in Austria, shows that horses generally prefer this arrangement too, and not just because this is how they are trained.

The researchers compared two groups of horses: one trained predominantly from the left and another trained equally on either side. They put them in various situations in which they interacted with people. The researchers found that most horses, regardless of how they were handled, favored their left eye and wanted to keep people in their left line of vision.

Farmer said a good example of this is when a horse refuses to longe to the right. This is often put this down to stubbornness, but Farmer said it is more likely the horse just wants to keep the person in its left line of vision.

“When this happens, the handler needs to give the horse the confidence to have the person on the right, not to punish it or force it,” she said. A horse that refuses to work with a person on the right might see him or her as a threat, and the trainer needs to be sensitive and patient to correct that perception