A major international research project, published on 2nd July, has explored how riders around the world perceive ‘sidedness’ in their horses, and the findings could reshape how we think about straightness, training, and equine welfare.
The study, led by Russell MacKechnie-Guire and supported by a team of international experts, including Animalweb’s Dr David Marlin, investigated laterality, the scientific term for left–right preference or asymmetry. In humans, this is most commonly seen as handedness. In horses, laterality can manifest as a preference for turning, bending, or using one limb over another.
So What Is Laterality?
Laterality refers to the natural or developed tendency for animals, including horses, to favour one side of their body. This may be motor-based (such as using one forelimb more), sensory (preferring to look or listen with one eye or ear), or even rooted in brain hemisphere dominance. While some horses may be born with these preferences, others may develop them through how they are handled, ridden or trained. For example, always mounting from the left or leading from one side can influence a horse’s physical development over time.
Although many riders and trainers talk about horses being “stiff on one side” or “falling in on a circle”, the underlying reasons have remained unclear–until now.
An International Effort with Over 2,300 Respondents
The online survey garnered more than 2,300 valid responses from horse owners and riders worldwide, making it the largest-ever study of equine laterality from the rider’s perspective. Participants shared detailed observations about their horse’s movement, hoof shape, shoulder symmetry, and responses to ridden and lunging exercises.
Key findings included:
- Horses were more commonly perceived to be stiffer or weaker on the right side.
- Many horses were easier to lunge and bend on the left rein.
- Asymmetries in mane direction, hoof angles, and shoulder prominence were frequently reported.
- However, a significant number of horses were also described as largely symmetrical.
These insights support the idea that while sidedness is common, it varies significantly between individuals, and not all horses display a clear left or right bias.
What Does This Mean for Training and Welfare?
Straightness is a fundamental part of the classical training scale, and many equestrian disciplines penalise lack of alignment or balance. But if horses naturally develop sidedness – or acquire it through human handling – then understanding this better is essential for training fairly and effectively.
The study’s authors highlight that recognising and managing laterality may reduce the risk of training-related injuries and improve overall horse comfort and performance.
Dr David Marlin, who contributed to the study through his work with Animalweb, says, “This is a brilliant example of how rider observations, when gathered at scale, can provide new scientific insights. We now have a clearer picture of how widespread laterality is and what patterns emerge across different horses.”
Read the Study
The full research paper, International Survey Exploring Rider-Perceived Sidedness of the Horse, is open-access and available here: Follow Link
