A neighborly neigh is processed in a different way than other whinnies, meaning that horses have brain side preferences for sounds, according to a new study by French researchers.

The phenomenon, known as “auditory laterality,” has previously been shown in humans, dogs, and some other vertebrates. But this new research is the first to reveal auditory laterality in ungulates, or hoofed animals.

Whereas the left hemisphere is clearly dominant for the processing of sounds that are familiar and normal, such as whinnies from nearby neighbors, both sides of the brain deal with sounds that are new or which emit an emotional response, according to the researchers. This could be a whinny from an unknown horse or one from the same social group, respectively.

 

Students Sarah Boivin and Haifa Benhajali record which ear the horse uses to listen to whinnies and other sounds.

“It was clear in our studies that horses do not have the same level of attention when they hear a horse they know compared to a horse they don’t know,” said Alban Lemasson, PhD, professor-researcher in the Animal and Human Ethology Laboratory at the University of Rennes and co-author of the study.

Twelve study horses were tested with iPod recordings of various whinnies played back at a distance of 10 meters (30 feet) behind the horse. The recorded whinnies represented three groups: members of the horse’s social group, nearby neighbors not in the horse’s immediate social group, and strangers completely unknown to the horse. A fourth test was made using white noise as a control. The horses showed