Thirty years ago the development of the child’s self was observed within the dyadic mother-child relationship. Since the Infant Research studies, D. Stern’s "intersubjective concept£ and that of the "primary triangle" by E. Fivaz - Depeursinge and A. Corboz- Warnery, the paradigm was extended to the triadic relationship that includes the father figure. Triadic competence is a specific competence and not a generalization of dyadic competence. Recent (2010) experimental studies by some italian authors, on the fetuses planning in twin pregnancies, will confirm the hypothesis of social pre-wiring in utero. These studies, together with their theoretical premises, may support a further hypothesis: in the development of self- twin is present the dyadic and the triadic competence, also the quadriadic one’s. This can be easily generalized to any polidiadica family dimension, recovering the importance of the phratry in the self- development, both in utero and in the following family and social, enviroments and processes.
Keywords: Quadriade, self-twin, order of geniture, polidiadica family dimension, gift of the damage.