Array properties and conservation of number performance with retarded adolescents and young adults

A group of 31 institutionalized retarded adolescents responded to 18 conservation of number tasks. Within the range of each row containing 4 to 6 items, there was no significant effect on performance with variations in the total number of items or the numerical difference between rows. Unexpectedly, pre- and posttransformed arrays did not cause significant differences in judgment errors. When significant differences (p less than .01) did appear between transformed and untransformed arrays, it seemed to be due to a one-to-one correspondence existing in one of the arrays and not in the effect of a transformation. The optimal performance under one-to-one correspondence conditions and the observed, orderly decrease in correct responding was explained as a function of the number of contradictions in the stimulus array. The explanation of judgment errors being caused by contradictions between numerosity and length and/or density cues was interpreted within Brainerd's (1973a, 1973b) theory of the development of early number concepts.