Irish researchers identified a unique link between equine motor laterality, or "handedness," and specific characteristics of facial hair whorls (trichoglyphs): right-handed horses had significantly more clockwise whorls whereas whorls were more likely to flow in a counter-clockwise direction in left-handed horses.

"It has long been speculated that most horses experience some degree of motor laterality in that they prefer one lead (or side) over the other," said co-author Jack Murphy, PhD, from the department of Life Sciences at the University of Limerick. "Riders tend to find that most horses have a 'preferred' side and gallop, jump, and work better on either the left or right rein."

The concern is that laterality could predispose performance horses to lack balance, which is not a desirable trait and could be a safety issue for novice riders.

"If trainers were able to identify if horses were left- or right-handed from the outset, then employing specialized individual training programs with these horses might contribute to a well-balanced athlete." –Dr. Jack Murphy Murphy explained, "If trainers were able to identify if horses were left- or right-handed from the outset, then employing specialized individual training programs with these horses might contribute to a well-balanced athlete." It appears that one simple, non-invasive way to establish lateral preferences in the horse is to look at the flow of hairs in the horse's facial whorls. This theory stems from a variety of studies that have found correlations between facial whorl features and various characteristics such as temperament, spermatozoa morphology, and handedness.

The purpose of the new study was to determine the relationship, if any, between the direction of flow (orientation) of the facial hair whorls and the incidence (and direction) of motor laterality in a test population of horses.

In total, 219 sound horses with only single facial whorl were included. Experienced equine trainers that were blinded to the nature of the study evaluated each horse to determine if the horse was well-balanced, right-handed, or left-handed based on lead preference while performing a variety of activities.

According to Murphy, significantly more horses were either right- (95/219) or left-handed (104/219) compared to only 20 horses that were "well balanced." The left-handed horses were primarily males (73/95) while female horses were more commonly right-handed (56/104).

Facial hair whorls might be the key to knowing which way a horse naturally prefers to work.

In terms of whorl pattern, 114 of the 219 horses had counter-clockwise whorls, 82 had clockwise whorls, and only 23 had radial whorls. The well-balanced horses did not have any difference in whorl pattern and in fact, they were likely to exhibit a higher incidence of radial facial hair whorls than expected purely by chance alone. "We also identified a significant association between laterality and facial hair whorl pattern," reported Murphy. "Left-handed horses had more counter-clockwise whorls and right-handed horses had more clockwise whorls."

Hair patterning and brain development occur in tandem while the embryo develops in utero and further studies in this area might provide valuable insight into behavioral and neurobiological development in horses. Other studies will also focus on if, how, and why particular training regimes can influence specific motor laterality trends in horses.

The study, "Facial hair whorls (trichoglyphs) and the incidence of motor laterality in the horse," is scheduled to be published in an upcoming edition of the journal Behavioural Processes.