The Mental Deficiencies

Abstract

T HE modern concept of mental deficiency derives its connotations from various disciplines. Sociology contributed from the earliest times the observation that there exists a group of individuals who, since childhood, are socially incompetent and incapable of adequate self-support. With the development of mental testing which permitted of an estimation of various grades of intelligence, the concept gained recognition that social incompetence is often associated with defective intellectual development. Following scientific advances in the field of medicine, it became increasingly clear that some diseases occurring during fetal life or in infancy may eventually result in lesions of the brain with consequent mental defect. Finally, with the advent of the science of human genetics the relevance of genetic factors in determining deviations of intelligence was made understandable.