RESUMO
The salience of various precursory requirements for the formation of symbols is discussed. The conclusion is drawn that several necessary precursors could be assumed, and two experiments are described that were designed to test for the presence of these precursors in autistic children compared to matched retarded children. First, there was a study of the children's ability to imitate and form internal images, and then there was a study of their development of a concept of object permanence and ability to anticipate. These studies led to the conclusion that the autistic children could form internal images but seemed to lack the ability to manipulate them in a purposeful and meaningful manner, as reflected in their inability to show symbolic imitations and their lack of tendency to use elements of their perceptions that might allow prediction of future events. The findings are discussed in terms of cognitive and social development.