A Dynamic Systems Approach to
Diagnostic Measurement of SLI
Paul van Geert
University of Groningen
A dynamic system is a structure of interacting forces. Structure refers to a relatively stable form of order and coherence of the properties of the system at issue. An interacting force is any variable that can affect—and can be affected by—some other variable. An important and maybe also the most interesting property of dynamic systems—at least of an important subclass that is worth studying—is that such systems of interacting forces show a spontaneous increase in structure and order. This spontaneous increase in structure (order, size, complexity, coherence, etc. ) is the consequence of a consumption of energy that flows through the structure of interacting components (e.g., in the case of a plant, solar light, nutrients, etc. ). The technical name of this spontaneous increase in order is selforganization.
In this chapter, a dynamic systems approach to SLI assessment is presented. First of all, the notion of self-organization in normal and defective language development is explained. In addition, a dynamic systems approach to SLI is proposed, starting from iterative models of long-term change. The dynamics of interacting growth processes within developmental language disorders is also explored. The chapter ends with implications for diagnostic measurement of SLI. Both the nature of psychological variables and the approach to diagnostic measurement in terms of a variable-by-characteristicness approach are reviewed from a dynamic systems perspective.