Rhythmically bouncing a ball with a racket is a seemingly simple task, but it poses all the challenges critical for coordinative behavior: perceiving the ball's trajectory to adapt position and velocity of the racket for the next ball contact. To gain insight into the underlying control strategies, the authors conducted a series of studies that tested models with experimental data, with an emph...

Three experiments illustrate how a task-based approach and dynamical modeling of a perceptual-motor task can provide a useful framework for understanding functional and dysfunctional behavior. In the chosen task, subjects held a racket and bounced a ball rhythmically in the air with invariant ball amplitude. As such, the task could be cast into a mechanical model that encompassed the movements ...

Asymmetric volatility refers to the stylized fact that stock volatility is negatively correlated to stock returns. Traditionally, this phenomenon has been explained by the financial leverage effect. This explanation has recently been challenged in favor of a risk premium based explanation. We develop a new, unlevering approach to document how well financial leverage, rather than size, beta, boo...

The lesser short-tailed bat (Mystacina t. tuberculata) has been found in 18 locations in indigenous forest in North Island since 1961, mainly in Northland kauri forest (including Little Barrier Island), on the volcanic plateau (including Tongariro National Park), Urewera National Park and in Tararua Range. In South Island this bat has only been reported once since 1961, in North West Nelson For...

Controlling for idiosyncratic volatility, large stocks earn higher returns than small stocks. Idiosyncratic volatility is positively related to return, but negatively related to size. Failure to control for idiosyncratic volatility generates a downward omitted variable bias, leading to the widely documented negative size-return relation. We explain the two contrasting sizereturn relations in a ...

This paper discusses the role of knee positioning and range-of- motion on the closed-stance forehand tennis swing. The analyses of tennis swing mechanics were performed using a computer model comprised of a full-body model of a human and an inertial model of a racket. The model was driven by subject forehand swings (16 female college-level subjects) recorded with a high-speed digital motion ana...