LEFT-HANDEDNESS.

Hauraki Plains Gazette, Volume XXXIX, Issue 5257, 28 March 1928, Page 4

LEFT-HANDEDNESS.

SURPRISINGLY PREVALENT.

THEORY OF DEVELOPMENT.

Left-handedness is surprisingly prevalent. Some authorities estimate it as high as 4 per cent, of the population ; whatever the total, males predominate largely over females.

Discussing the question in the “Empire Review," Dr. Leonard Williams says our simian, cousins are truly ambidqxterous, but in m.an there is no such thing as real ambidexterity. Speech is man’s most salient characteristic, and it its, possible that his dextrality is associated w'ith this bioilogically peculiar development. Speech is represented on the left sidei of the brain. The muscular movements on the right side of the body are dependent upon centres on the left side of the brain. This association between, speech and right-sided muscular power is shown in the case of a “fit of apoplexy.” When the haemorrhage devastates, the left brain there ensues a paralysis of the musclei?, on the right side of the body, with concomitant loss of speech. Wneh the Haemorrhage is into the right brain there is paralysis of the muscles on the left side of tne body, Out no ilos's of speech. Another reason for dextrality is that man soon learned the left side of nis body was more vulnerable than Ms right. He did not know that his heart was on the left side, but experience taught him that penetrating wounds of the left chest were more instantly fatal than similar wounds of the right chest, so he carried his shield in his left hand and wielded his weapon with his right. This greater activity of the right arm muscles would mean a correspondingly greater development of the left brain cemtres, so that, ultimately, not only the muscles of the right a'rm, but all the. muscles on the right side of the body, would become stronger than those on the left side.

A large number of left-handed people are afflicted in various, degrees with stammering or other defects of that kind. The number is so large that the association cannot be fortuitious. This would suggest that, when the 'speech centre is situated in. the right brain instead of in the left brain it fails to reach the normal degree of development. A great many theories have been advanced in explanation of righthandedness, some of which are very far-fetched. Inasmuch as there is no anotomical reason why people should favour the right hand, the practice has been confidently ascribed to the imitation of a habit begun, by chance and aimlessly continued. Some authorities have advanced the idea that right-handedness, is due to the position of the infant in arms ; by which one hand is restrained and the other allowed to develop. There are certain ’crafts, notably that of the surgeon, in which some approach to ambidexterity is an outstanding advantage. it is said that the really expert pick-pocket is always ambidextrous. Sir James Crichton-Browne deprecates the attempt to educate people into ambidexterity. He says: “We cannot, I believe, get rid of our righthandedness, try h'ow we may. Ambidextral culture, useful enough in respect of some few special movements in some few specially employed persons. must, on the large scale, tend to confusion.