Apart from the obvious benefit of being able to ride horses for film (actors being cast based on their ability to ride), there’s far more substance to this method.
When performing we aim to develop concentration and connection with our acting partner to create a remarkable and truthful performance. It is the actor’s ability to communicate beyond the words what makes camera close ups powerful.
What could be a stronger method of developing these skills than working with another creature with a mind of its own?
A horse doesn’t understand your words but it does understand the tone of your voice and body language. It understands when you are angry or happy. When you ride a horse, it makes you notice in an instance if you loose concentration.
Riding and working with horses relaxes your body and mind and boosts you with powerful energy, which you then bring into the acting performance. If you are rather a phlegmatic character with issues keeping focused, riding will force you to develop and maintain concentration and connection.
It is no wonder that so many great actors tend to work intensively with horses. Just to name few: Viggo Mortensens, Mary Kate Olsen, Russell Crow, Kaley Cuoco, Jeremy Irons…