If laughter is contagious among humans, are similarly happy feelings contagious among horses? A group of Swiss researchers has taken a closer look at this theory—and it seems that horses can share and transmit their emotions through their whinnies.

“Our preliminary results suggest that horses are able to distinguish positive-emotion whinnies from negative-emotion whinnies among familiar horse voices, and that they react accordingly with positive and negative emotions,” said Elodie Briefer, PhD, of the Institute of Agricultural Sciences and the Swiss Federal Institute of Technology, in Zurich. “Those emotions are often expressed in response whinnies.”

Familiarity among horses appears to be a key component in this ability to communicate emotions vocally, Briefer said during her presentation at the Swiss Equine Research Day, held April 16 in Avenches.

In their study, Briefer and her colleagues studied 18 horses during different vocalization and listening tests. The horses came from various stables, so they were familiar with some, but not all, of the participating equids