Fact: Yes, they are. The more time you put into them the more you get back. They are just as intelligent as any dog and learn just as fast. They are smart and need mental stimulation. Also if you treat them with respect, the same respect you would give a child, they will turn out loving and happy animals. Treat them like a cute play-thing to dress up, aggravate them because its funny, or never teach them the different between right and wrong because they are just too cute, you will have a horse with an attitude that will bit, kick, and act like a brat. Think about it. If you don't teach them what is right and what is wrong they will try to get away with anything and show you that they are the boss. A Mini will not respect someone that will not tell them NO. Treat and train your mini like how you would want a hound dog to act, not like a dog that people want to put in their purse because its a fashion accessory.
Miniature horses have a hierarchy just like any pack or herd animal. And like people mini horses are not going to get alone with every single person. I have heard of Mini horses biting at the legs of their owners. This is something they adults to younger horses to show that the young ones are not showing respect and need to know their place. In other words, the horse is trying to put the person in their place.