Scientists haven't given too much attention to the significance of horse snorting before now.
The expulsion of air through the equine nose has normally been connected with "clearing phlegm, flies or other irritants".
But now researchers in France say that these blow-outs are a key indicator of what's going on in the equine mind.
They found horses living in relaxed environments produced far more snorts than those in stressful conditions.
Understanding when a horse is feeling happy, scientifically, is quite difficult. Cats are easy by comparison; their purring is a clear sign of contentedness.
Horses give off conflicting signals - their heart rates increase at the anticipation of food, but decrease during grooming, something that humans generally believe they enjoy.
Some people believe that horses being playful are showing they are happy. But researchers say that this isn't always the case, as play can be a "coping mechanism" when horses are faced with unexpected events, and it may also be a way of reducing social tension in the group.
In this study, the scientists wanted to test the anecdotal idea that snorting in horses occurs more often in positive situations.
So what exactly is a snort?
Experts say that horses produce three different non-vocal sounds, all by passing air through their large nostrils. Who knew?
Snores are very short raspy sounds produced when a horse is examining something new. Blows are described as short and very intense exhalations and are associated with vigilance or alarm.
Horses snorted far more when they were out in pasture than when they were in a stall. Among riding school horses, snorts occurred at a rate of around five per hour which was about half of what the horses in naturalistic conditions produced. These were also correlated with positive behaviours such as ears pointing forward. When the researchers looked at other measures of welfare and stress they concluded that "the more snorts emitted the more they were in a good welfare state".
The riding school animals also produced more snorts during their limited time out in pasture. No animal was recorded snorting when it was being aggressive. Eight horses in the stalls produced no snorts while they were being monitored.