I have known this along time, but have you ever noticed a horse's ears? 

When a horse's ears are pointing in front or towards you, it means he/she is listening to you. 

When it is pinned back, it means he/she is annoyed, upset, or angry with something. 

Sometimes when his/her ears are back, it could mean he/she is happy and would show off by running around, jumping, or do something wild because he/she feels happy. (sometimes other horses near by will start to do the same because they become happy as well). 

There are also many other ways the ears go, which you can almost read there ears. But it is not only about the ears that can talk. There are other ways a horse can say things with. 

(Picture by Noelle Harris)