The brain is supposedly divided into two halves: the left half, which is the thinking and reasoning side; and the right half, which is the instinct and survival side. The Parelli's use the terms "right brained" if the horse is acting fearful, and "left brained" if they are using thinking or reasoning skills.
Most horses seem to prefer people to be on their left side, whether it is leading, grooming, tacking up, clipping, bathing, etc. Some are spookier at objects on their right side, but are fine with objects to their left.
What is your explanation for this? Do horses react more from things on their right because it is the fearful right side of their brain, or because humans have made them that way by doing things mostly from the left?
I'm on the "humans make them that way" side, but I am interested in hearing everybody's opinion. Thanks!