Can horses recognize each other from the sounds of their voices? The answer, according University of Sussex, England, researchers, is yes.

The researchers discovered that horses, like humans, use a variety of clues to recognize each other: it’s a combination of sound, visual recognition and smell.

The results were published in Proceedings of the National Academy of Sciences of the United States of America on December 15, 2008.

The study, by Leanne Proops, her dissertation supervisor Dr. Karen McComb and mammal communication researcher Dr. David Reby, focused on 24 horses at Woodingdean livery yard in Sussex and Sussex Horse Rescue Trust in the U.K.

The researchers observed one horse while another was led past. A different horse’s neigh was played on a loudspeaker at the place where the second horse disappeared from view. The researchers measured the time it took for the test horse to look in the direction of the loudspeaker.

They found that horses responded more quickly and looked for longer in the direction of the mismatched calls, which indicated that the mismatched combination violated the horse’s expectations.

"Given that the stimulus horse was out of sight when the vocal cue was heard, it is likely that the test horse was accessing or activating some form of multimodal memory of that individual's characteristics," says Proops.