Spectrum of power laws for curved hand movements Dongsung Huh and Terrence J. Sejnowski http://www.pnas.org/content/early/2015/07/02/1510208112.abstract In curved hand movements around ellipses, the speed tends to scale inversely with the curvature with a power law having an exponent of -1/3. We examined whether this well-known regularity in motor planning holds for more general shapes. Using an optimality principle, we identified a set of basis shapes, each with a single characteristic angular frequency, which subjects drew with power laws whose exponents ranged from 0 to -2/3. More general movements exhibited linear mixtures of power laws. The speed of arbitrary doodling movements with a broad spectrum of frequencies could also be predicted from the curvature with high accuracy. Terry -----