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The maintenance of upright posture involves constant adjustment to external and internal perturbations. This balancing act is often assumed to be an automatic process, but studies suggest that cognitive processes, parti- cularly attention, are necessary for the control of posture. The current study examines the role of attention in balance using a dual-task paradigm. Twenty-four healthy young adults performed a sit-to-stand (STS) task on either a stable or unstable platform while performing a secondary cognitive task of counting backwards aloud. Movement of the upper and lower body was analyzed using the largest Lyapunov exponent (λ1) and standard deviation (SD). Results replicated earlier ndings (Gibbons, Amazeen, & Likens, 2018) that the transition from sit to stand was marked by increased variability and a temporary destabilization of postural control. Participants exhibited greater movement variability overall on the unstable platform (large SD), but small λ1 indicated that movement was controlled. During second task performance, SD increased for the upper body only. Further research is necessary to understand the interaction between attention and balance in young adults. 

The principle of dynamical similitude—the belief that the same behavior may be exhibited by very different systems—allows us to use mathematical models from physics to understand psychological phenomena. Sometimes, model choice is straightforward. For example, the two-frequency resonance map can be used to make predictions about the performance of multifrequency ratios in phys- ical, chemical, physiological and social behavior. Sometimes, we have to dig deeper into our dynamical toolbox to select an appro- priate technique. An overview is provided of other methods, including mass-spring modeling and multifractal analysis, that have been applied successfully to various psychological phenomena. A final demonstration of dynamical similitude comes from the use of the same multifractal method that was used to extract team-level experience from the neurophysiological data of individual team members to the analysis of a large scale economic phenomenon, the stock market index. Continual development of analytical methods that are informed by and can be applied to other sciences allows us to treat psychological phenomena as continuous with the rest of the natural world. 

In activities such as dancing and sports, people synchronize behaviors in many different ways. Synchroni- zation between people has traditionally been characterized as either perfect mirroring (1:1 in-phase synchronization, spontaneous synchrony, and mimicry) or reflectional mir- roring (1:1 antiphase synchronization), but most activities require partners to synchronize more complicated patterns. We asked visually coupled dyads to coordinate finger move- ments to perform multifrequency ratios (1:1, 2:1, 3:1, 4:1, and 5:1). Because these patterns are coordinated across and not just within individual physiological and motor systems, we based our predictions on frequency-locking dynamics, which is a general coordination principle that is not limited to physiological explanations. Twenty dyads performed five multifrequency ratios under three levels of visual coupling, with half using a subcritical visual information update rate. The dynamical principle was supported, such that multi- frequency performance tends to abide by the strictures of frequency locking. However, these constraints are relaxed if the visual information rate is beyond the critical informa- tion update rate. An analysis of turning points in the oscil- latory finger movements suggested that dyads did not rely on this visual information to stabilize coordination. How the laboratory findings align with naturalistic observa- tions of multifrequency performance in actual sports teams (Double Dutch) is discussed. Frequency-locking accounts not only for the human propensity for perfect mirroring but also for variations in performance when dyads deviate from mirroring.