Summary.—Changing ideas on intelligence testing and the heritability of intelligence are followed through a fifty‐year period. Common criticisms of intelligence tests are examined, but it is concluded that intellectual tests will continue to be of value in diagnosing the strengths and weaknesses, particularly of exceptional children.The arguments about the extent to which heredity and environment contribute to the development of intelligence are traced through a turbulent period. The evidence presented is consistent with an environmental contribution of over 20 per cent of the variance, although the precise value is not considered to be as important as recognising that both genes and environment have very substantial effects on the measured intelligence of children. The inaccuracies detected in some of the research reports on the heritability of intelligence are not considered to invalidate the argument as a wh