Dynamic systems theory conceives of development as a self-organizational pr
ocess. Both complexity and order emerge as a product of elementary principl
es of interaction between components involved in the developmental process.
This article presents a dynamic systems model based on a general dual deve
lopmental mechanism, adapted from Piaget and Vygotsky. The mechanism consis
ts of a conservative force, further strengthening the already-consolidated
level, and a progressive force consolidating internal contents and procedur
es at more advanced levels. It is argued that this dual mechanism constitut
es one of the few basic laws of learning and change and is comparable to th
e laws of effect and of contiguity. Simulation studies suggest that this du
al mechanism explains self-organization in developmental paths, including t
he emergence of discrete jumps from one equilibrium level to another. S-sha
ped growth, and the occurrence of co-existing levels.