Color vision in horses (Equus caballus): deficiencies identified using a pseudoisochromatic plate test.

This research study aimed to better understand the color vision capabilities of horses using a pseudoisochromatic plate test. The study findings suggest that horses have a similar visual spectrum to humans suffering from red-green color deficiencies, meaning they are dichromats.

Research Methodology

• The researchers conducted this study by using a pseudoisochromatic plate test. This test is known for its effectiveness in studying color vision in humans, including both children and adults. However, this is the first time this test was used on a nonhuman species.
• The pseudoisochromatic plate test uses stimuli composed of dotted circles of various colors set against a dotted background. In this test, the color of the circles aligns with different types of color deficiencies, specifically anomalous trichromacy and dichromacy.
• The test subjects in this study were four horses, who were assessed using a two-choice discrimination task.

Findings of the Study

• The findings showed that all the horses were able to successfully identify the gray circles and demonstration circles. However, none of the horses could discern the protan-deutan plate or the individual protan or deutan plates.
• Interestingly, all of the horses were able to discriminate the tritan plate, suggesting certain color perception capabilities.
• From these results, the researchers concluded that horses have dichromatic vision, which means they can see two primary colors. This type of vision is similar to the red-green color deficiencies found in humans.

Significance of the Study

• Prior to this study, research investigating equine color vision produced inconsistent results, leaving the topic controversial and unstable. This study steps forward, pioneering a new way of testing color vision in animals, and specifically illuminates a more precise understanding of color perception capabilities in horses.
• The newfound comprehension regarding horses’ color vision fundamentally holds potential implications for horse training, welfare, and also tool and environment design where horses are involved. This knowledge may help create more optimally stimulating and meaningful environments for horses.