ABSTRACT
Intelligence, a concept within the area of individual differences, reduces itself to two essentials, the power of the mind, and the skills through which this power expresses itself. For the purposes of scientific analysis, and to demonstrate the differential effects of various environmental influences on the development of intelligence, it is useful to think in terms of factors, each representing a particular degree of abstraction. Nutrition, particularly in the earliest years of life, may have a permanently enhancing or depressing effect. Group tests which utilize verbal, numerical and perceptual skills will give a fair approximation, depending on the diversity of this material. Tests of the Binet and Wechsler type are the most adequate for the measurement of mental power, because of the diversity of mental skills which they involve. Group tests which utilize verbal, numerical and perceptual skills will give a fair approximation, depending on the diversity of this material. A multitude of circumstances, including differences in nutritional levels, complexity of material environment, parental outlook and education, schooling facilities, affect intellectual growth.
