Human Body as a Nonlinear Dynamical System

<p>The human body is a non-linear and non-equilibrium open system that transfers energy to and from the external world, interacts with other elements, and develops and self-organizes over time while maintaining a temporary order. Because the human body is never constant, the time series of human movements are always subject to fluctuations. These time series often exhibit self-similarity (fractal structure), and the scaling exponent changes according to the stages of motor learning as well as the motor control characteristics. The scaling exponent can also be an index that reflects individual dynamics in various movements and actions including standing, walking, and talking. In recent years, attempts have been made to quantify the global coordinative relationships between people by using the scaling index related to fractality. The methodology for analyzing and describing non-linear and non-equilibrium open systems is the dynamical systems approach, describing the changes in the coordination patterns of various rhythmic movements―such as dancing, and music performance―as bifurcation phenomena associated with changes in the order parameters. The emergence of behaviors different from those of individuals alone has been observed in motor coordination tasks between humans, and these phenomena have been reproduced by the coupled oscillator system models. From the standpoint of viewing the body as a nonlinear dynamical system, it is possible to understand a variety of phenomena on a wide range of spatio-temporal scales, including not only individual human behaviors but also the social behaviors of human groups, in a unified manner. This approach to finding scale-free laws that transcend the boundaries of matter, life, and society is expected to be developed in the future as a complementary methodology to the position of attempting to explain human behavior from microscopic elements.</p>