Results
IQ
Child – Adult cohort. IQ change over time: Although there was a decline in IQ scores for the group as a whole (Best estimate Child IQ = 86.2; SD = 13.94; Adult IQ = 70.24, SD = 33.90; r = .12 (ns), t = 3.5; p = .001), this apparent decrease was attributable to 15 individuals who were unable to be tested directly in adulthood and for whom follow-up assessments were based on the Vineland only. For the remainder of the cohort, there was little change in average IQ scores and correlations between test scores over time were moderate to high. When first seen as children, only around one third of the group was able to score on the Wechsler tests or to obtain a verbal IQ score on any formal measure. However, as adults, the number able to complete these assessments had increased and group means in adulthood were very similar to those in childhood. The mean scores of individuals who were assessed on these measures both as children and adults had actually increased, with marginally significant improvements in Verbal IQ and Wechsler FIQ and PIQ scores