An increase in a human's heart rate affects the heart rate of the horse they are leading or riding, researchers at the Swedish University of Agricultural Sciences recently reported.

Linda Keeling, PhD, and colleagues tested horses and riders to see if humans inadvertently communicate fear and anxiety to horses. Using heart rate as a fear indicator, the researchers asked 20 people with varying levels of horse experience to walk and ride 10 horses from Point A to Point B four times. The researchers told participants an umbrella would open as they rode or led the horse on the fourth pass. The umbrella never opened, but heart rates in both horses and humans increased during the fourth trip between the points, when the human expected the umbrella to open.

"The increase in the horses' heart rates probably means that they are more alert and prepared to react to any potential danger," Keeling said. "In the wild, horses are adapted to respond to other animals in their group. A startle reaction is more likely when the horse is very alert."

If you are a nervous person leading or riding a horse, your nervousness might increase the likelihood of the "spook" that you are anxious to avoid.

The study, "Investigating horse-human interactions: the effect of a nervous human," was published in the July 2009 issue of The Veterinary Journal. The abstract is available on PubMed.