A follow-up developmental study of hypothesis behavior among mentally retarded and nonretarded children

To clarify the roles of IQ and mental age (MA) in hypothesis behavior, MA-matched subjects at three levels of IQ (70, 100, and 130) and three levels of MA ($\text{5}\text{1}\text{2}\text{, 7}\text{1}\text{2}\text{,}\text{and}\text{9}\text{1}\text{2}\text{years}$) received blank-trial discrimination learning problems using procedures designed to discourage position-oriented responding. With position responding discouraged, earlier findings were contradicted in that no hypothesis measure showed a main effect of IQ. This suggest that previously reported IQ group differences in hypothesis behavior may not reflect cognitive deficits inherently linked to low IQ, but instead may reflect the influence of specific methodological factors. The finding and interpretation are consistent with Zigler's (American Journal of Mental Deficiency, 1969, 73, 536–556) “developmental” theory of retardation and inconsistent with the general “difference” position. In additional findings, the predictions that subjects at all three MA levels would use hypotheses, and that retarded children from special-education classes would use hypotheses more often than retarded children “mainstreamed” in classes for the nonretarded were confirmed.     

The Rorschach and structured tests of perception as indices of intellectual development in mentally retarded and nonretarded children

In a study of the developmental significance of certain perceptual activities, the Rorschach and four structured tests of perception were administered to five groups of children at various CA, MA, and IQ levels. All three Rorschach measures were significantly related to MA, as were all four of the structured tests. The Childrens' Embedded Figures Test was the best predictor of MA; it accounted for 52% of the variance, while the six remaining measures yielded nonsignificant increments to a multiple regression equation. In a factor analysis the four structured tests loaded on one factor (51% of total variance), while the three Rorschach variables loaded on a second (17%); MA loaded on both (.669 and .447, respectively). In an additional finding, Zigler's “developmental” hypothesis that level of development and not IQ determines cognitive competence, received partial support from 13 of 14 statistical tests.