In search of differentiations in the development the picture sign

The differentiation between expression and content is fundamental in the concept of signs. Even if the notions of signs are often revised, due partly to the attraction of a semiotic approach from markedly disparate objects of study, a common apprehension of the distinctive character of meanings by sign is its dual nature. (Saussure 1968, Piaget 1951, 1966; Vygotsky 1999; Sigel 1978; DeLoache 2000) Signs can be understood as objects of meanings, to some one, which also extend their perceptual expressions or sensations. All signs imply sign processes; the sign function is due to a mental capability or inclination in the sign user. But meaning is not equivalent to sign function and it is an important issue in the study of semiotics to investigate the differences and conditions between meanings that are merited to sign relations and meanings that are not. (Sonesson) To study the development of a sign function in the child does not only tell us something about child development, but also about signs.
To understand pictures involves to master sign relations. From my studies of the child becoming sign minded, and particularly learning to understand pictures, it has become clear that the differentiation between expression and content is a too broad an outline to be informative. In the perspective of child development the generic distinction between expression and content in the mature sign needs more specific distinctions to capture the emergence of such a delicate cognitive competence as the ability to master sign functions.