Conceptualising nonlinear dynamic systems for health psychology research

The application of nonlinear dynamic models and techniques to psychological research has revealed that systems behaviour often defies many commonly held assumptions about the world (Eidelson, 1997). Consideration of nonlinear dynamics systems has shown (i) that studying phenomena in isolation from their overarching context does not yield a complete understanding of the whole system (Barton, 1994) and (ii) the behaviour of systems (whether simple or complex) are frequently nonlinear and/or discontinuous (Barton, 1994; Guastello, 2002). Chaos and complexity are terms which have entered the psychological research vocabulary relatively recently. Yet, in other disciplines underlying theoretical constructs and developments have been brewing and evolving for decades. To date, several theoretical models in health psychology that implicitly or explicitly link change with determinants of health have been developed or adopted (e.g. Janz & Becker, 1984; Madden, Scholder Ellen, & Ajzen, 1992; Ogden & Hills, in press; Prochaska & DiClement, 1984). Such models have produced a substantial body of research and knowledge on the relationships between biopsychosocial factors and health outcome. The adequacy of traditional research methods in psychology for answering the questions that they purport to answer has often been questioned (e.g. Barton, 1994; Cox, Karanika, Griffiths, & Houdmont, 2007). The present paper explores nonlinear dynamic systems and their relevance to health research. It starts with the question why nonlinear dynamic systems should be used in health psychology research. It then moves to a delineation of some key concepts (complexity, emergence, homeostasis and self-organisation, nonlinearity and dynamics, chaos and unpredictability)