Dynamical systems show changing patterns of action over time, but retain characteristics of an integrated whole. A stable system retains important characteristics even in the face of perturbations that disturb the behavior of specific elements. A system’s distinct parts are not isolated from each other, thus the characteristics of the whole entity cannot generally be deduced from each of its components. Applications of both information theory ( Attneave, 1959 Yockey, 2005) and chaos theory ( Elbert et al., 1994 Guastello, Koopmans, & Pincus, 2009 Rossler & Rossler, 1994 Weiss, Garfinkel, Speno, & Ditto, 1994) have been made to the biological and behavioral sciences, and the present article draws upon insights from this work.įor the purposes of this article, we define a system as a variety of elements that interact with one another to form a whole entity. In recent years, mathematical versions of systems theory have been applied in biology and behavioral science, as described below.īecause Wiener’s theory had limited predictive power, it was soon combined and supplanted by theoretical systems with greater complexity, such as Shannon’s information theory ( Shannon & Weaver, 1949), which incorporates concepts of channel capacity, noise, and entropy (here reflecting the uncertainty in prediction rather than the conventional meaning implying dissolution of order), as well as chaos theory ( Gleik, 1987 Kellert, 1993), which emphasizes deterministic nonrandom but complex nonlinear relationships among a large number of co-occurring processes, for which statistical prediction is possible. This model served as a heuristic for describing behavioral, economic, biological, and astronomical systems, among others ( Mindell, Segal, & Gerovitch, 2003 Wiener, 1948). ![]() However, a mathematical approach for aircraft communication and control systems had been articulated by Wiener as early as the 1940s ( Wiener, 1948, 1961). Without the ready availability of mathematical models for the social and biological sciences, a nonmathematical approach to systems theory was prominent in early biofeedback work, and was well articulated by Schwartz and colleagues ( Schwartz, 1981 Schwartz et al., 1979). Empirical hypotheses derived from this approach are presented, including that moderate stress may enhance health and functioning.Ĭoncepts of ‘cybernetics’, ‘systems’ (dynamic and otherwise), ‘complexity’, ‘chaos’, ‘catastrophe’, and ‘oscillation’ have long been part of discourse in the behavioral, social, and biological sciences. Resonance in negative feedback loops can help stimulate oscillations and exercise control reflexes, but also can deprive the system of important information. Examples are presented of oscillatory processes in heart rate variability, and regulation of autonomic, thermal, pancreatic and central nervous system processes, as well as in social/organizational systems such as marriages and business organizations. Positive as well as negative feedback loops are important for system function and stability. Resonance effects can be used to strengthen modulatory oscillations, but may obscure other information and control mechanisms, and weaken system stability. Resonance can occur in systems with negative feedback loops, causing high-amplitude oscillations at a single frequency. External system stressors such as disease, psychological stress, injury, or interpersonal conflict may perturb a system, yet simultaneously stimulate oscillatory processes and exercise control mechanisms. ![]() This modeling approach can be applied to a diverse range of phenomena, including cardiovascular and brain activity, mood and thermal regulation, and social system stability. ![]() Unstable systems, often associated with poor health, are characterized by absence of oscillation, random noise, or a very simple pattern of oscillation. ![]() Feedback produces oscillatory activity, and the complexity of naturally occurring oscillatory patterns reflects the multiplicity of feedback mechanisms, such that many mechanisms operate simultaneously to control the system. Control systems can be characterized as open or closed systems with feedback loops. This paper applies newer methods of control systems modeling to the assessment of system stability in health and disease. Systems theory has long been applied in psychology, biology, and sociology.
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