Multifractal fluctuations in joint angles during infant spontaneous kicking reveal multiplicativity-driven coordination

Damian G. Stephen, Wen Hao Hsu, Diana Young, Elliot L. Saltzman, Kenneth G. Holt, Dava J. Newman, Marc Weinberg, Robert J. Wood, Radhika Nagpal, Eugene C. Goldfield

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Previous research has considered infant spontaneous kicking as a form of exploration. According to this view, spontaneous kicking provides information about motor degrees of freedom and may shape multijoint coordinations for more complex movement patterns such as gait. Recent work has demonstrated that multifractal, multiplicative fluctuations in exploratory movements index energy flows underlying perceptual-motor information. If infant spontaneous kicking is exploratory and occasions an upstream flow of information from the motor periphery, we expected not only that multiplicativity of fluctuations at the hip should promote multiplicativity of fluctuations at more distal joints (i.e., reflecting downstream effects of neural control) but also that multiplicativity at more distal joints should promote multiplicativity at the hip. Multifractal analysis demonstrated that infant spontaneous kicking in four typically developing infants for evidence of multiplicative fluctuations in multiple joint angles along the leg (i.e., hip, knee, and ankle) exhibited multiplicativity. Vector autoregressive modeling demonstrated that only one leg exhibited downstream effects but that both legs exhibited upstream effects. These results confirm the exploratory aspect of infant spontaneous kicking and suggest chaotic dynamics in motor coordination. They also resonate with existing models of chaos-controlled robotics and noise-based interventions for rehabilitating motor coordination in atypically developing patients.

Original languageEnglish (US)
Pages (from-to)1201-1219
Number of pages19
JournalChaos, Solitons and Fractals
Issue number9-10
StatePublished - 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Applied Mathematics
  • Statistical and Nonlinear Physics
  • General Physics and Astronomy
  • Mathematical Physics


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