Handedness in Horses

by
James Rooney, D.V.M.

We all know about left and right handedness in man and the relationship of handedness to dominant halves of the cerebrum: right hand-left cerebral hemisphere; left hand-right cerebral hemisphere. One can't make too many mistakes since the dominant or preferred hand is easily discerned. It is not so simple with horses.

To begin to discuss this in horses one must first define what is meant by handedness. Anyone is free to define it anyway one chooses, of course, and I choose to say that most horses are left-handed because most horses turn to the left, the near side, more readily than they do to the right, off, side. That tendency has been recognized for, literally, centuries. Horses are preferentially handled from the near side; draft teams were usually trained to turn left. Now, one can say that the horse works better to the left because man has always taught them to do so. If that were the case, why did man do that? I believe that man did that because that was the easiest way to get the horse to do what was desired. Go with the flow one might say.

Without getting into too much detail (you can find that in The Lame Horse, 2nd Edition), this suggests that the horse is usually right brain dominant, the dominance being manifest as the ability to support weight most easily and efficiently when turning to the left. That is a matter of proprioceptive reflex chains which are, again, discussed at some length in The Lame Horse.

You all know that the better/best dressage horse is one which can work equally well to the left or to the right. You also know that very few (any?) horses begin training able to work equally well in either direction. What is usually said is something like the horse is "stiff" to the off side and needs "suppling" work to loosen it up when moving in that direction.

In fact, the horse is no stiffer in a physical or mechanical sense to the off side than the near side. The training process does not change the animal physically; rather it changes him mentally. The training process teaches ambidexterity. Probably very few of you are fully ambidextrous though you may well be able to do many things with both hands. It is unusual, however, to be able to write well with both hands. The problem with the horse may be less difficult since its handedness manifests through reflex chains, not requiring conscious thought. What one is really doing by the training is convincing the horse by repetition that, indeed, it can move to the right as easily as to the left. Some horses learn quickly; others never learn at all. Have you ever learned to write with the other hand? If you have, you will know that it is difficult and takes a long time and is quickly forgotten if not practiced regularly. And, indeed, like the horse that never learns to move well to the right, you may never be able to write legibly with the "wrong" hand.

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