The conversation had already begun.… At a small equine training center outside Kyoto, a young trainer named Haru had an unusual habit. Every morning, before saddling the horses, she talked to them. “Good morning, Kaze. You slept well?” “Come on, Momo. We have work to do today.” The other trainers sometimes laughed. “You know they don’t understand Japanese, right?” Haru always smiled. “Maybe not the words.” Yet she continued. And strangely enough, the horses seemed to work better when she did. Modern research gives part of the explanation—but not the one Haru’s colleagues expected. Horses can learn particular human words through conditioning, and experiments have found that they can discriminate a taught word even when it is spoken by an unfamiliar voice. Human vocalizations directed at horses can also acquire consistent meanings within particular riding communities, while pitch, duration, and intonation alter how those sounds func...