ABSTRACT
The development of intelligence tests and of the concepts of intelligence quotient (IQ) and mental age (MA) are too well known to require detailed exposition here (e.g., Goodenough 1949a). The impact on the field of mental retardation was enormous. In 1924, Fernald commented that “The theory and practice of mental testing and the discovery of the concept of mental age did more to explain feeble-mindedness, to simplify its diagnosis and to furnish accurate data for training and education, than all the previous study and research from the time of Séguin” (p. 209). It was in the field of mental retardation that intelligence testing flourished in its early years before being applied to individuals of higher intellectual levels.
