The link between motor laterality and emotion is well established in humans and rodents, Now researchers studying cognitive bias in horses found that they differ in their laterality depending on the emotionality of test situations. When horses were stressed, or challenged with frightening objects such as umbrellas, they displayed increased left laterality, a indicator of pessimism.
Positive, optimistic horses are far more easy to train and to handle.”
Source: EQUUS, October 16, 2023. Link.