Final answer:
A handler can interpret a horse's behavior and emotions by carefully observing its non-verbal cues, such as the positioning of its ears, eyes, nose, and mouth.
Step-by-step explanation:
By observing the ears, eyes, nose, and mouth of a horse, the handler can interpret the horse's behavior and emotions. Much like the example where a dog uses its master's whistling to determine direction, a handler can learn to understand a horse's non-verbal cues. For instance, a horse with ears pinned back may be signaling irritation or anger, while a horse with ears forward is likely attentive or curious. Observant handlers can use this information to respond appropriately, ensuring a safer and more effective interaction with the horse.