The Concept and Measurement of Adaptive Behaviour

Abstract

The second part of the current definitions of intellectual disability requires that the individual should have significant limitations in adaptive behaviour. Before the advent of IQ tests in the early twentieth century, definitions had largely been based on a lack of coping skills; for example, in 1910 the US government announced that:

Feeble-mindedness has been broadly defined as comprising all degrees of mental defect due to arrested or imperfect mental development as a result of which the person so affected is incapable of competing on equal terms with his normal fellows, or of managing himself or his affairs with ordinary prudence. (c.f. Scheerenberger, 1983)

However, once IQ tests were introduced definitions tended to be in terms of measured intellectual ability. By the middle part of the twentieth century it was clear that basing the definition on measured intellectual ability alone resulted in a number of problems. In the US it was noted that a disproportionate number of people from lower social classes and ethnic groups were being classified as mentally deficient, which led to concerns from civil rights groups in the early 1960s (c.f. Greenspan 1997). It was also apparent that many people who have measured IQs in the low range were not only able to look after themselves but also were able to play a useful role in society, for example, Gelb (2004) points out that during the Second World War, when there was a demand for men, many people with low IQs successfully served in the US armed forces.