The authors present a dynamical multilevel model that captures changes over time in the bidirectional, potentially asymmetric influence of 2 cyclical processes. S. M. Boker and J. Graham's (1998) differential structural equation modeling approach was expanded to the case of a nonlinear coupled oscillator that is common in bimanual coordination studies in which participants swing hand-held pendulums but is also applicable to social systems in general. The authors' nonlinear coupled oscillator model decomposed the fluctuations into a competitive component, unique to each individual variable, and a cooperative component that captured bidirectional influence. The authors' model also generated an index of the symmetry/asymmetry of bidirectional influence. Together, the models are useful quantitative tools for the study of interacting, changing processes.

These and previous results support the hypothesis of increased neuroplasticity and prefrontal cortex function following ACT and, to a smaller extent, following VC. Both ACT and VC appear to be associated with cortical benefits, but based on current and previous results, ACT seems to maximize the benefits.

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Examining the effects of diapers and other external constraints on infants' leg movements may affect how we collect motor control research data, dress infants to allow optimal movement in the home, and administer therapeutic interventions for infants with motor impairments. To address this issue we supported 12 healthy infants (2-4 months) on an infant-sized treadmill in each of 4 conditions: wearing nothing (None), a swim diaper (Swim), a disposable diaper (Diaper), or a combination of diaper and research recording equipment (All). We recorded the trials with a digital video camera and behavior coded number of steps and step type (alternating, parallel, double, or single steps) to assess both quantity and quality of movements. Infants produced similar numbers of steps in a predominantly alternating step pattern (high quality) during the None, Swim and Diaper conditions, but both quantity and quality of stepping decreased in the All condition. Our results suggest that diapers alone do not alter stepping patterns significantly, but sufficient additional weight and clothing beyond the diaper can affect movement frequency and quality in young infants.Everyone who has worn tight, uncomfortable clothing can attest to how these items affect both movement amplitude and willingness to produce some types of actions. Popular magazines contain numerous articles on how to select clothing that will allow comfortable movement (Meyer, 1997), wick away sweat from the body during exercise (Olsson, 1998), improve sport performance (O'Driscoll, 2008), assist in weight loss (Enamait, 2008;Johnson, 2005) or protect from the elements (Beers, 2006;Thein, 1995). Despite the wealth of informal observations, scientific publications on how clothing constrains movement in adults are sparse, and in infants nonexistent. Researchers have investigated how clothing constrains movement only in cases of specialized clothing for the military or fire fighting, where limitations on movement cost lives (Malley et al., 1999;Patton, Bidwell, Murphy, Mello, & Harp, 1995). Infancy is another crucial time when bulky clothes and diapers could constrain movement enough to delay exploration and performance of nascent motor skills. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Advertisers of disposable diapers claim that their brand reduces bulk around the legs so infants can crawl or walk better than in competitors' styles, but research either has not been conducted or is not publicly available. Advancements in diaper technology, including contouring and development of absorbent materials have reduced the bulk aroun...

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