Developmental concept of idiocy.

In dominant definitions of mental retardation, researchers have insisted on the diagnosis being restricted to conditions manifested during the developmental period. However, even in the 19th century, this was only one of several conceptual options, some of which did not exclude adult brain injury or dementia. Events in the 19th and early 20th centuries, particularly with the growth of institutions, scientific study, and, later, intelligence testing led to these other options being excluded. Here, I discuss the proposal that current definitions are highly contingent on factors that are neither essential nor necessary. Although not arguing for any specific changes to current definitions, I do argue that theoretical options should be kept open and that dominant ones should be questioned.