Changes in IQ, environmental and individual factors: a follow-up study of educable mentally retarded children

A group of 28 former pupils of Special Schools for the EMR was tested both in childhood and at adult age. Information about the subjects' situation as children was available from the local school files. Pupils who had experienced the most serious problems as children were less retarded at adult age than persons who had experienced few or none problems. Three persons with impaired hearing showed also a marked increase in I.Q. scores. The results may give support to Clarke's and Clarke's hypothesis that the effects of an early unstimulating environment are not necessarily irreversible.