2. _Disuse or Neglect of Faculties._—The impairment of mental powers through disuse is one of the most common phenomena of psychology. Men are much more colour-blind than women, because they exert less the faculty of distinguishing hues. Persons who do not practise memorising soon lose the power.
In the history of nations this has been most conspicuous in the neglect of the military spirit; Carthage yielded to Rome, and Rome to the barbarian, chiefly because a distaste for personal exposure in combat led each nation in time to depend on mercenaries for defence. For centuries in China the vocation of the soldier has been looked upon as inferior to that of the scholar or the statesman; and, however just this might be in the abstract, it so weakened the national integrity that the vast Sinitic empire is now tottering to ruin.
Disuse may arise from two conditions: the one, from neglect and overattention to other faculties; the other, from absence of opportunity.
Both are abundantly represented in ethnic psychology. Of the former, I have just given instances; while of the latter the deliberate avoidance by large groups of certain areas of mental life are examples in point. Thus, the Society of Friends (Quakers) have for two hundred and fifty years expelled the cultivation of the fine arts from their education. The result is a loss of the æsthetic faculties, but a remarkable gain in other directions—such as sobriety, longevity, business success. Whether the compensation is sufficient seems, however, to be decided in the negative by the Friends themselves.
Other examples present themselves. The aristocracy of Siam regard all forms of work as so degrading that they allow their finger-nails to grow five or six inches in length to prove that their hands have never been soiled with labour. Needless to say that this disuse of their muscles is followed by atrophy of their brain-cells, so that they are an emasculate and enfeebled group. The theory of concentration and disuse of faculties in the group led to the system of castes, the most striking example of which is in India, where they are divided upon race lines. The white Brahmans are the priests, legislators, scholars, and diplomats; the red Rajpoots are the warriors and chieftains; the yellow Mongols are the commercial and agricultural class; while the black Dravidians are the mechanics and herdsmen. Each caste adopts its special branch of activity and avoids that traditionally belonging to another caste.