Heuristic techniques for the analysis of variability as a dynamic aspect of change

Due to the influence of dynamic systems and microgenetic perspectives, variability is nowadays often seen as an important phenomenon that helps us understand the underlying mechanisms of development. This paper aims at demonstrating several simple techniques that can be used to analyse variability in data of developing (or learning) individuals. These techniques will be illustrated by applying them to a time serial dataset of early child language (to be specific, the emergence of grammatical preposition use). First, we show some descriptive techniques that are essential first steps for generating hypotheses. Also, we propose a measure that expresses qualitative variability. Furthermore, we demonstrate how resampling techniques can be used to test the presence of performance peaks, which may be important because they indicate the emergence of new abilities. Finally, we show the use of a technique that is especially useful for exploring interactions between ordinal variables (the State Space Grid, or SSG). With this illustration, we hope to encourage researchers to take a more exploratory approach to variability in their data and to develop methods directed at analysing dynamic aspects of change.