An Exploratory Model of Play

Play is defined as a state of experience in which the actor's ability to act matches the requirements for action in his environment. It differs from anxiety, in which the requirements outnumber the ability, and from boredom, in which the requirements are too few for the ability level of the actor. Games are reviewed with illustrations from a cross-cultural context of traditional and modern societies. It is suggested that games of skill, strategy, and chance all share structural characteristics that allow the player to limit his experiences so as to maximize the play experience as defined. Further theoretical implications are drawn from the model in terms of the relationship of individuals and the social system.     

Strong growth limitation of a floating plant (Lemna gibba) by the submerged macrophyte (Elodea nuttallii) under laboratory conditions

1. The asymmetric competition for light and nutrients between floating and submerged aquatic plants is thought to be key in explaining why dominance by either of these groups can be stable and difficult to change. 2. Although the shading effect of floating plants on submerged plants has been well documented, the impact of submerged plants on floating plants has been poorly explored hitherto. 3. Here, we used laboratory experiments to examine how submerged plant (Elodea nuttallii) alter nutrient conditions in the water column and how this affects the growth of floating plants (Lemna gibba). 4. We demonstrate that, at higher nutrient concentrations, Lemna is increasingly likely to outcompete Elodea. 5. Under low nutrient concentrations (0.1–2 mg N L^?1) Elodea can strongly reduce the growth of Lemna. Growth of floating plants virtually stopped in some of the experiments with Elodea. 6. Extremely reduced tissue N, Mn, chlorophyll and elongated roots indicated that the growth inhibition of Lemna by Elodea was predominantly caused by the latter’s impact on the nutrient conditions for floating plants. 7. These results strengthen the hypothesis that submerged plants can prevent colonization of a lake by floating plants.