Right-Handedness is the property or condition of being right-handed. The cause is not known. Some contend that it is racial habit, growing out of the left hand being used for unclean purposes and, therefore, not fit for eating, salutation, etc. This has not been proven. Others, like Charles Reade, contend that man should be ambidextrous, and that it is a duty in athletics to preserve the balance between the hands. The propensity in man to use the right hand in preference to the left is by some attributed to the lack of perfect symmetry in the body. If the body could be folded over from a medial line so that each organ of the one side should lie exactly on a corresponding organ of the other, the bodily structure would be highly fitted, in a mechanical sense, for the equal use of either limb, and ambidextral individuals would be the rule. The centre of gravity in the body of the average person is a little to the right of such a medial line. This makes the right side the heavier. From a series of experiments the greater weight has been estimated at about 15 ounces. On this fact is founded the mechanical theory of right-handedness, the predominance of the right hand over the left; or, more generally, of the limbs of the right side over those of the left. The extra 15 ounces, however, may be a result not a cause to right-handedness. The three-lobed right lung is more capacious and receives more air during an inspiration than the two-lobed left lung. The liver during inspiration swings toward the right side, shifting the centre of gravity farther to that side. In violent muscular exertion there is more air proportionally inhaled by the lung of the side which sustains the exertion. Under exertion of the right side the larger lung is better filled than the smaller, and the centre of gravity is removed till it is found in a line passing through the right foot; so that the right leg and foot afford a steadier basis of support than the left would do under similar circumstances. Through the greater use of the right lower limb the right upper limb comes to be preferred. In the case of a light weight, slung on the arm, the equilibrium of the body is better maintained by carrying it on the left side. If the weight be a heavy one, borne on the left shoulder, the burden is really beine supported very much by the right limb, owing to the natural curve of the body toward the right side, while sustaining the pressure.
In a very few cases left-handedness has been found to accompany transposition of the viscera. But cases of genuine left-handedness far exceed in number such instances of transposition. Ferrier's researches have proved that when we see with the right eve we see with the left side of the brain. Hereditary left-handedness, if there be such a thing, may be due to the greater development of the right side of the brain. It is practically certain, says Bastian, that the great preponderance of right-handed movements in ordinary individuals must tend to produce a more complex organization of the left than the right hemisphere. Some think that in the evolution of man right-handedness has probably been a late acquisition. The oldest discovered records of the human race, however, suggest man to have been right-handed. Pre-historic weapons are those of right-handed individuals; many tools, etc., now in use are made for the right hand.
Right-handedness in man appears to be more persistent than the corresponding quality in lower animals. Naturalists, who observe that adult monkeys catch nuts more with the right hand, that the African elephant digs more with the right tusk, or that the Carolina parrot has a preferential claw for grasping, tell us that these habits are subject to exceptions more numerous than those of left-handedness in human beings. Another view of the whole subject is taken by some psychologists, who maintain the probability that the tendency to right-handedness is due to unrecognized spiritual causes, which underlie all phenomena of life. Since we do not know what life is, nor even how and why we are sentient creatures, the problem is wholly beyond our reach, and the ingenious theories only demonstrate man's fondness for speculation.