This thesis of this book is that it's possible to learn the nonverbal language of horses, and that such knowledge would enable a person to train a horse without resorting to physical force (see horse breaking).
The front flap says:
Monty Roberts is a real-life horse whisperer - an American original whose gentle training methods reveal the depth of communication possible between man and animal. He can take a wild, high-strung horse who has never before been handled and persuade that horse to accept a bridle, saddle, and rider in thirty minutes.
Roberts claimed to have been beaten by his father, but according to other sources, such as Roberts' aunt, Joyce Renebome, and cousin, Debra Ristau, in their book, "Horse Whispers & Lies", Marvin Roberts was a kind and compassionate man. Roberts' brother, Larry Roberts, also refuted the claims of child battering.