After a training session, your horse goes back to his resting area and looks in his water bucket for a drink. The water level is at the halfway mark. So, does your horse think his bucket is half full or half empty?

Yes, even horses can be optimistic or pessimistic, according to Swiss equine behavior scientists who have developed a test to find out whether horses are one or the other, or somewhere in between. In fact, the researchers recently used the test to determine how positive and negative reinforcement affect horses’ outlook: Does it put them in an optimistic or pessimistic mood?

They found that while negative reinforcement fosters more negative emotions, the horses actually become more optimistic once negative reinforcement training ends than with positive reinforcement—at least in this particular study, said Sabrina Briefer Freymond, MSc, a researcher at Agroscope-Swiss National Stud in Avenches.

“Animal welfare is commonly linked to physical state and mental state,” said Briefer Freymond. “And because animals cannot tell us how they feel, it’s really important—and it’s a real challenge—to measure emotions.” Briefer Freymond presented her work at the 9th Conference of the International Society for Equitation Science (ISES), held July 17-19 at the University of Delaware in Newark.

In her experiment, Briefer Freymond and her fellow researchers used a novel method—called the “judgment bias approach”—to test horses’ level of optimism. Scientists have used judgment bias tests successfully with other species, but never before with horses.