1950s and 1960s: The Medical Model Prevails.
A New Perspective Develops.

Going into the second half of the 20th Century, the prevailing definitions of mental retardation and perspectives of service focused almost exclusively on deficits in the individual. Those definitions combined issues about general intelligence and the individual's ability to cope with the demands of everyday life. At the same time, a concept (the principle of normalization) was developing in Scandinavia. It would have a profound impact on definitions and perspectives in North America

The Medical Model and an Emphasis on Deficiency

Edgar Doll
Edgar Doll

Edgar Doll's 1941 definition set the standard for many of the more medical definitions of the century. Doll identified six criteria generally considered essential to an adequate definition and concept of mental retardation:

  • social incompetence
  • due to mental subnormality;
  • which has been developmentally arrested;
  • which obtains (remains) at maturity;
  • is of constitutional [physical] origin; and
  • is essentially incurable.

This basic definition soon evolved into determinations of the levels of disability. Most are linked to the measurement of I.Q. or Intelligence Quotient. "Subnormality" meant below the normal I.Q. of 100. Over the years, there have been important changes in how far below normal someone's I.Q. score had to be before being considered "mentally retarded".

Early IQ Testing
Early IQ Testing

IQ

3