I realized horses have personality when I bought one and I had one, who's now out to pasture, a horse named Drifter. Before that, I was a city boy. Horses, I used to go out to the LaBagh Woods and ride at a stable once every two years or something; no idea about horses. Dogs, I knew, had personalities, but not horses.
As filmmakers, we want the audience to have the most complete experience they can. For example, I interviewed Stanley Kubrick years ago around the time of '2001: A Space Odyssey.' I was going to see the film that night in London, and he insisted I sit in one of four seats in the theater for the best view or not watch the film.