Actually, this is the field I am studying, and I have worked for an equine therapist for 5 years now, just as a horse leader. She does physical therapy, I am going into emotional/mental type therapy.
Horses are amazing aren't they? Big or small they can sense when they are needed to help make someone's day. I have had numerous experiences witnessing such acts, but the one that jumps out is a therapy horse that I helped train. His name is Smokey and he is an arab cross. For a regular rider on a trail, smokey needs a firm but steady hand as he is very flighty and spooky, but for therapy, he is an absolute angel. He has had numerous children on him (being led around) and it is amazing to watch him. As I am leading him, I can always tell if the child is getting off balance. Of course the therapist puts him back in place, but smokey knows it is happening and gently nickers to me, like he is saying "hey, he needs some readjusting." At the same time he will slow down or stop, which is unheard of for him under normal circumstances. He walks slow to make sure the kid is okay, when normally he rushes and has a very quick walk.
Smokey is pretty head shy, but when those little kids get off of him, and walk over to him (usually on braces, since most of these kids have trouble walking) he just puts his nose on the floor, closes his eyes, and lets them pet him all over. It is amazing to watch the transformation this horse undergoes as he understands he is carrying precious cargo. It never gets old to watch