Editor's note: This article is part of TheHorse.com's ongoing coverage of topics presented at the 2012 International Society of Equitation Science conference, held July 18-20 in Edinburgh, Scotland.

It can be a nerve-wracking experience for some riders, but when you hand your horse over to another rider, do not fear. At least, according to new study results, you don't need to fear for him. The researchers found that horses that are used to just one rider don't appear to be any more stressed or afraid of new things if they're mounted by a different rider; they might, however, be less cooperative.

"Many owners state that they share a very special bond with their horse, and I would certainly be one of them," said Uta König von Borstel, PhD, equitation scientist at the University of Göttingen in Germany, who oversaw the field work of Nora Krienert, MSc. "Our research indicates that horses might have greater trust, but not less fear, when they're with familiar riders." König von Borstel presented the research at the 8th International Society for Equitation Science conference, held July 18-20 in Edinburgh, Scotland.

König von Borstel and Kreinert employed three different types of horses in their research:

• Privately owned horses usually ridden by a single rider;
• Mounted police horses usually ridden by a single rider; and
• Riding club horses ridden by several different (but regular) riders.

New obstacles or objects were placed in the riding arena. Each of the 47 horses was ridden past or over these obstacles once under its regular rider (or one of its regular riders in the case of the club horses) and twice under two different riders that the horse didn't know. The tests were run in random order to prevent habituation from affecting the results.

The team measured the horses' heart rates, behavior, and time to approach the objects during the three tests. They also measured the riders' heart rates.

Upon reviewing their results, the team found:

• Privately owned horses took just as much time--which, generally speaking, was significantly longer than it was for mounted police horses and for riding club horses--to approach the unknown objects with their regular riders as with an unknown rider. König von Borstel said this wasn't a surprising finding, however, as most riding club horses and mounted police horses are specifically selected and trained to be calmer around unfamiliar stimuli.
• The mounted police horses took "a lot less time" to approach the unknown objects when they were with their regular riders than with unfamiliar riders, König von Borstel said. Interestingly, these horses actually had lower heart rates with unfamiliar riders than with their regular riders, she said, adding that at this time the explanation for that phenomenon is not understood.
• The mounted police horses and the privately owned horses tended to show more negative behavior when approaching the objects with an unfamiliar rider compared to a familiar rider, König von Borstel said, while riding school horses showed very little difference among all riders.
• König von Borstel noted a distinct influence of the rider on horses in all categories: "The higher the rider's heart rate, the longer the horse took to approach the object," she said. "And the higher the rider's heart rate, the higher the horse's heart rate, and that was even more significant with familiar riders."

In regards to the heart rate differentials, König von Borstel said this could be simply a physical connection, in that the rider might be working harder to control a more excited horse. However, it can't be denied that there might be a psychological connection as well, she said.

"Some of these results could just be an indication of different personality types, or even just an effort of the horses to try to get away with not having to approach the object because they don't want to," König von Borstel said. "But our findings could also be interpreted as horses having a greater trust in their (regular) riders. They may be less fearful with a familiar rider, but they don't show that in their behavior."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.