Thought provoking and beyond metaphor

In recent years computational ideas have had a pervasive influence on cognitive psychology. Not only have many detailed computational models of cognitive processes emerged, but numerous computational metaphors and analogies have entered into the parlance and the thinking of those studying cognition. Notional processing resources, memory buffers, and subroutines are often invoked in an attempt to understand human perception, thought, and action. The computational approach to cognition has led to many significant insights. But the analogy fails to capture crucial aspects of mental processes, most notably the dynamic way that cognitive operations unfold. The contributors to Mind as Motion believe that there is a framework better suited to understanding and modelling the key features of human cognition, and this they term the dynamical approach.

The dynamical approach takes its name and inspiration from the study of dynamical systems in mathematics, systems whose behaviour is equated with the change of numerical states over time. Each chapter provides a sample of recent work using the dynamical approach, illustrating the application of dynamics to the study of cognition in accessible and often thought-provoking ways. We are given a lucid introduction to dynamics which assumes only a basic knowledge of calculus and matrix algebra, but instead relies on graphical and qualitative descriptions to provide the reader with a feel for the behaviour of a range of simple dynamical systems. Concepts such as attractor and bifurcation, stability and catastrophe, characterise the behaviour of dynamical systems and, it is argued, the dynamics of cognition.

The dynamical approach is a paradigm in the Kuhnian sense to compete with the established computational approach. While a dynamical approach to cognition was proposed by Ashby as long ago as 1952, it was the computational approach which dominated thinking in AI and cognitive science. Rather than the algorithmic manipulation of internal symbols, the dynamical approach views cognitive processes as the behaviour of nonlinear dynamical systems. The computational approach is criticised for its failure to capture the temporal aspects of cognitive operations; its serial transitions between discrete states being contrasted with the multiple simultaneous interactions displayed by dynamical systems.

Mind as Motion is aimed at a general audience of cognitive scientists. Contributions on topics ranging from visual perception and sensorimotor coordination to auditory perception, language production and event recognition catalogue the way in which the dynamical systems approach has contributed to progress in particular fields. The relationship of the dynamical approach to more established methods is covered in the introduction. For example, some of the chapters, such as Elman's paper on language processing, use neural network models which fall into both the "dynamical" and the "connectionist" camps. However, a single philosophy unites all the contributions - the belief that natural cognitive systems will be best understood by using dynamics.

Colin Clifford is a research student in psychology, University College London.