The emergence of the symbolic function at the end of the sensorimotor period plays an important role during the development of the human infant. It is the beginning of the attainment of signs and symbols – depicting an item (an object, a person, an event, etc.) by a differentiated signifier (language, mental image, symbolic gesture, etc.) specifically used for this particular representation.
Although the symbolic function cannot be tested directly, various behavioral manifestations, implying the use of differentiated signifiers, reflect it. Authors generally agree on the various behavioral manifestations appearing during the second semester of the second year of life:
“generative” language (Piaget, 1936);
deferred imitation (Piaget, 1945) or real imitation (Guillaume, 1925);
the communicative function of immediate imitation (Baudonnière & Michel, 1988; Asendorpf & Baudonnière, 1993; Hart & Fegley, 1994);
pretend play (Piaget, 1945; Kagan, 1981);
stage 6 understanding of object permanence (Piaget, 1936);
recognition of the specular self-image (Zazzo, 1975, 1977, 1985; Lewis & Brooks-Gunn, 1979).
These behavioral manifestations allow us to study the emergence of the symbolic function. The question is to determine whether these new competences emerge simultaneously, resulting from a common transformation, or successively. If the symbolic function appears as a singular modification influencing many behaviors, it should result in the simultaneous emergence of the various behavioral manifestations. On the contrary, if this emergence proceeds step by step, the different behaviors should emerge not synchronously but progressively, eventually in a hierarchical way.