We like to think that some horses have exceptional, if not extra-sensory vision, with the capacity to see monsters in the bush or ghosts under fences, but this is far from the truth. Their eyesight is pretty limited compared to humans.
Horses are dichromats, which means they see a reduced number of colours compared to humans, who are trichromats (see diagram). This translates to horses seeing the world in a palette of blues and yellows, and they find it more difficult to detect subtle differences in natural colours. Traditionally, many of the colours and materials used in cross-country fences are rustic colours such as reds, orange, greens and natural wood, which horses likely find difficult to distinguish.
From his base at Exeter University in the UK, where he is part of the Sensory Ecology and Evolution Group, Professor Martin Stevens has focused more than 15 years of research on how animal vision works and how this influences their behaviour. “Most of my work had until recently been focused on the natural world, but I started to become very interested in how knowledge of animal vision could help inform various areas of human life, including animal training, welfare and safety,” explains Professor Stevens, whose eventing research project was partly funded by British Eventing, the governing body for the sport in the UK.
“Horse sports immediately seemed to be an area where such knowledge and methods could have great value to complement what was known already by those in the industry, since much of the obstacles and environment is still based on human perception.”
In the course of his eventing research, Professor Stevens and his team analysed the contrast of important elements of cross-country fences by taking digital images at five affiliated British events, covering 15 courses from 80cm to four-star (now five-star) level. They looked at a number of areas, including the contrast in colours between the foreground and groundline, and the top of the fence and the background. They also looked at variations between colours and foreground materials like sand or grass, and lighting conditions according to the weather at the time.
The researchers found that conspicuousness of the groundline influenced the fault rate at the two highest levels (equivalent to CCN3* level and above), but was not influential at the lower levels between EvA80 and CCN2*. Furthermore, the conspicuousness of the top of the fence influenced the fault rate at the middle two levels (equivalent to CCN2* and CCN3*), but not at the lowest or highest levels. In analysis, the scientists proposed that the fault rate at the lowest levels was more likely linked to the training and education of the less experienced horses, rather than explained by limitations to a horse’s vision and thus his understanding of the fence design.
Professor Stevens and his team suggested that yellow, blue or white matt paint would improve visibility of fence components such as the groundline or top of the fence.
British international course designer, Captain Mark Phillips, supports the idea of clearly contrasting fence edges. “What we give the horse to enable it to read the leading edge of the fence is hugely important,” he says. “The leading edge has got to have enough contrast with the surroundings so that the horse can clearly understand the question.”