Human Balancing Tasks: Power Laws, Intermittency and Levy Flights

Peer reviewed encyclopedia article. FP wrote the section on virtual stick balancing, JLC the sections on stick balancing on the fingertip and Levy flights. Full text available online. "Synonyms: Human stick balancing; Virtual stick balancing; Balance control dynamics; Lévy flights to improve balance control; Skill acquisition in stick balancing; Characterization of motor learning in continuous tracking tasks. Definition: In human stick balance intermittency is observed (Fig. 1). Here intermittency denotes the random alternation between phases with extremely low movement amplitudes and phases with high movements amplitudes. This type of intermittency is characterized by power laws in the distributions of corrective movements in real stick balancing and in virtual stick balancing (that is, balancing an unstable target on a computer screen). These observations are commonly seen as evidence which contrasts neurological control from standard engineered controllers..."