Abstract
This study was designed to elucidate collective dynamics in ball sports by developing an index to quantify team cooperation; it also aimed to confirm the validity of that index by applying it to actual game data. Cooperation within a team was quantified in terms of the team divergence coefficient (TD), which was expressed as team convergence-divergence during play. To evaluate use of space on the court or field, a team pressure-field (TP) was calculated as the sum of individual pressure-fields (IPs), based on the pressure-field model developed by Kijima (2008). The TD was then calculated from the TP using Shannon's entropy. We analyzed the relationship between the TD and team distance which was confirmed as a control parameter for pattern of game, by analyzing data from two actual field hockey games played by six-player adult and youth teams. The adult game has shown that it switched the cooperation patterns between divergence and convergence according to the team distance, however, the youth game has not shown. Our results suggest that the team distance would be considered as a control paramter for a team cooperation. We discussed a collective dynamics of team cooperation from a dynamical systems perspective.
