Associate Professor Ayaka Takimoto of Hokkaido University, graduate student Kosuke Nakamura of The University of Tokyo, and former Professor Toshikazu Hasegawa of The University of Tokyo have established that horses, like dogs, can read and understand human faces and emotions.
They found that horses who looked at human faces while listening to recorded voices were able to recognize when the face was happy, but the voice recording was scolding and knew that the voice did not match the face. They were able to recognize happy faces with happy recordings and angry faces with angry recordings.
What was also interesting was that it did not matter if the horse knew the person or not. They were still able to match the correct facial expression with the correct voice.
Horses do have strong communication capabilities. They can read the emotions of other horses using facial expressions, contact calls, and whinnies. With this in mind, it is not surprising that with their long association with humans, that they have learned to read us. It would be reasonable to assume that other members of the equine family have the capability to read us too.