Defending qualitative change: the view from dynamical systems theory.

A central controversy in developmental science, enflamed by nativist accounts, is whether development is best viewed as a series of qualitative or continuous changes. This article defends the notion of qualitative change from the perspective of dynamical systems theory (DST). Qualitative change within DST refers to the shift that occurs when a system goes from one attractor state through an instability into a different attractor state. Such changes occur on the second-to-second timescale of behavior. Thus, developmental analysis must always stay local, grounded in the real-time attractor states around which behavior is organized. This article also demonstrates that qualitative and continuous change should not be cast in opposition. They are aligned concepts that work together across multiple timescales.