DEVELOPMENTAL-CHANGES IN ACTION - THEORETICAL AND METHODOLOGICAL ISSUES

A tutorial is provided of how che concepts and methods of non-linear d ynamical systems theory and, in particular, catastrophe cheery can be of help in understanding the development of action. From this theoreti cal perspective, development is viewed as a complex, time-evolving pro cess in which new behaviours (e.g. reaching, walking, speech) are the produce of self-organization. Qualitative changes in behaviour are int erpreted-ex hypothesi-as discontinuous non-equilibrium phase transitio ns or catastrophes. In the context of the study of the development of prehension, it is illustrated how this interpretation can be investiga ted empirically by testing if specific transition criteria are satisfi ed. Once che presence of such criteria has been confirmed for the emer gence of a particular behaviour, the next step is to determine if a ca tastrophe model can be found chat applies to the data. Preliminary evi dence is provided that the developmental change in prehension during t he first six months of life is best described as a cusp catastrophe.