The early childhood curriculum is informed by a complicated array of developmental and learning theories. In recent times these theories have been most readily articulated in approaches to curriculum planning emerging from the Developmentally Appropriate Practice (DAP) guidelines and the project work in Reggio Emilia. Drawing on a common theoretical heritage, each of these approaches places a certain emphasis on ideas emerging from cognitive constructivism and developmental theory. This paper explores the nature of these theoretical informants as they are played out in both DAP and Reggio Emilia. Findings from a study aimed at examining educators' conceptions of cognitive constructivism and developmental theory as utilised by DAP are reported, with the responses by four educators regarding these understandings in relation to their developing awareness of the Reggio Emilia approach detailed. The paper identifies differences in orientation between the educators' conceptions of developmental theory and constructivism relative to DAP and Reggio, and indicates the potential value further research in this area holds for examining how common theoretical informants can be played out to different effect across early childhood curricula.