Summary.This is the first of two artioles whose object is to throw light on the development of, and retardation in, abilities by comparison of patterns of test scores with assessments of environment, both within and between certain contrasted cultural groups.A series of verbal tests is described, some group, some individual, which were applied to a representative group of 100 boys close to 11:0 years in South‐East England, and to a sample of fifty similar boys in the West Indies. These included tests of educational attainments, memorizing, vocabulary, and a battery of items based on Piaget's investigations of concept development. The latter was shown to be factorially complex. Mean West Indian scores varied widely, ranging from an English deviation quotient of 72 on Vocabulary to 94 on Spellin