SUSSEX, ENGLAND—Domesticated horses are able to distinguish between angry and happy human facial expressions, according to a study conducted by Amy Smith and Karen McComb of the University of Sussex. When shown angry human faces, the horses looked more with the left eye, which allows the right brain hemisphere to process threatening stimuli. (Dogs have also been shown to have a tendency to use the left eye when viewing negative human facial expressions.) The horses’ heart rates also increased more quickly, and they exhibited more stress-related behaviors, when shown the angry human expressions. “In this context, recognizing angry faces may act as a warning system, allowing horses to anticipate negative human behavior such as rough handling,” Smith said in a press release. “There are several possible explanations for our findings,” added McComb. “Horses may have adapted an ancestral ability for reading emotional cues in other horses to respond appropriately to human facial expressions during their co-evolution. Alternatively, individual horses may have learned to interpret human expressions during their own lifetime,” she explained. For more, go to "The Story of the Horse."