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Mixed Strategies (mixed + strategy)
Selected AbstractsEvolutionarily stable investment in secondary defencesFUNCTIONAL ECOLOGY, Issue 5 2005M. BROOM Summary 1Previous workers have suggested that the evolutionarily stable strategy (ESS) for investment in antipredator defences, such as toxins, will critically depend on the nature of expression of the defence. Specifically, it has been suggested that if the different levels of a defence are best described as a continuous variable, then this will lead to pure ESSs with all individuals in a population adopting similar defence levels; whereas defences that can only take on discrete levels will lead to mixed ESSs (featuring variation in defence within the population). 2Our principal aim is to determine the validity of these viewpoints, and examine how the pure and mixed strategies predicted by the two types of defences can be reconciled with practical and philosophical difficulties in defining any given defence unambiguously as continuous or discrete. 3We present the first model of a continuously varying defence that is solved explicitly for evolutionarily stable strategies. 4We are able to demonstrate analytically, that the model always has a unique ESS, which is always pure. This strategy may involve all members of the population adopting no defence, or all members of the population making the same non-zero investment in defence. 5We then modify our model to restrict the defence to a number of discrete levels and demonstrate that the unique ESS in this case can be either pure or mixed. We further argue that the mixed ESS can be a combination of no more than two defence levels, and the two levels in a mixed ESS must be nearest neighbour levels in an ordered list of the levels that the defence can take. 6This, in turn, means that the mixed ESS will be practically identical to a pure ESS if the discrete defence is fine-grained. [source] Price competition under universal service obligationsINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 3 2010Axel Gautier L13; L51 In industries like telecom, postal services or energy provision, universal service obligations (uniform price and universal coverage) are often imposed on one market participant. Universal service obligations are likely to alter firms' strategic behavior in such competitive markets. In the present paper, we show that, depending on the entrant's market coverage and the degree of product differentiation, the Nash equilibrium in prices involves either pure or mixed strategies. We show that the pure strategy market sharing equilibrium, as identified by Valletti, Hoernig, and Barros (2002), defines a lower bound on the level of equilibrium prices. [source] Hatching fraction and timing of resting stage production in seasonal environments: effects of density dependence and uncertain season lengthJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2001M. Spencer Many organisms survive unfavourable seasons as resting stages, some of which hatch each favourable season. Hatching fraction and timing of resting stage production are important life history variables. We model life cycles of freshwater invertebrates in temporary pools, with various combinations of uncertain season length and density-dependent fecundity. In deterministic density-independent conditions, resting stage production begins suddenly. With uncertain season length and density independence, resting stage production begins earlier and gradually. A high energetic cost of resting stages favours later resting stage production and a lower hatching fraction. Deterministic environments with density dependence allow sets of coexisting strategies, dominated by pairs, each switching suddenly to resting stage production on a different date, usually earlier than without density dependence. Uncertain season length and density dependence allow a single evolutionarily stable strategy, around which we observe many mixed strategies with negatively associated yield (resting stages per initial active stage) and optimal hatching fraction. [source] Probabilistic Voting and Accountability in Elections with Uncertain Policy ConstraintsJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 1 2007ADAM MEIROWITZ We consider accountability in repeated elections with two long-lived parties that have distinct policy preferences and different levels of valence. In each period the government faces a privately observed feasibility constraint and selects a publicly observed policy vector. While pure strategy equilibria do not exhibit tight control on government policy making, complete control is possible in mixed strategies. In optimal equilibria voters use reelection functions which depend on policy in a manner that causes the governing party to internalize voter preferences. In these optimal equilibria the voters use different reelection functions for different parties. [source] Road Slope Revegetation in Semiarid Mediterranean Environments.RESTORATION ECOLOGY, Issue 1 2007Part I: Seed Dispersal, Spontaneous Colonization Abstract The importance of neighboring vegetation as a seed reservoir for spontaneous colonization of adjacent road slopes was analyzed in a semiarid region of east Spain. Two independent methodological approaches were used to examine the relative contribution of seed from neighboring vegetation and the efficiency of different seed dispersal strategies in plant colonization. We first used a randomization test to compare floristic similarity between road slopes, neighboring flora, and local flora (the regional species pool found in the same climate and soil conditions as the road slopes). Second, we compared seed dispersal mechanisms of road slope vegetation with those of the surrounding area using frequency analysis. Species composition of road slopes was more similar to that of the flora of adjacent surrounding areas than expected by chance. Anemochorous (wind-dispersed) plants were over-represented in road slopes 8 years after road slopes were built. We concluded that seed dispersal from neighboring vegetation is an important factor in the vegetative colonization of road slopes. However, this initial species pool was also strongly shaped by the harsh environmental conditions of roadcuts and southern aspect. These results have important implications in road slope restoration because they suggest that naturally vegetated areas should be maintained adjacent to road slopes to enhance seed immigration from species adapted to local site conditions, which will accelerate the successional process. The application of this single reclamation strategy and mixed strategies that combine the use of natural colonization and soil amendment for road slope restoration in Mediterranean environmental conditions is discussed. [source] Impact of reducing intrinsic cognitive load on learning in a mathematical domainAPPLIED COGNITIVE PSYCHOLOGY, Issue 3 2006Paul Ayres This paper examines the effectiveness of instructional strategies that lower cognitive load by reducing task complexity (intrinsic cognitive load). Three groups of 13-year-old students were required to learn a mathematical task under different conditions. One group (Isolated) followed a strategy that used part-tasks where the constituent elements were isolated from each other (element isolation). A second group (Integrated) received whole tasks where all elements were fully integrated, and a third group (Mixed) followed a mixed strategy progressing from part-tasks to whole-tasks. Results indicated that the part-task strategy was effective in lowering cognitive load for all students, but only benefitted learning for students with low prior knowledge. In contrast, students with a higher prior knowledge learned significantly more having studied whole tasks during instruction compared with part-tasks. The mixed-mode method proved to be ineffective for both levels of prior knowledge. These results are discussed in terms of cognitive load theory. Copyright © 2006 John Wiley & Sons, Ltd. [source] Optimal Stealth Trading of the Insider and Expected Profit of the Mimicking Trader,ASIA-PACIFIC JOURNAL OF FINANCIAL STUDIES, Issue 3 2009Jaehyun Lee Abstract In this paper we perform theoretical and empirical analyses on the insiders' optimal "stealth" strategy and expected profits from mimicking trading when the insiders' trading information is publicly available. When insiders select a mixed strategy of AR (1) process as the information exposure strategy in a multi-period model, we find the optimal AR (1) coefficient that maximizes the insiders' profit is negative. Also, (1) the greater the transaction volume of mimicking traders in the market and the longer the information exposure period, the closer the optimum AR (1) coefficient becomes to ,1; (2) The larger the mimicking transaction volume, the smaller the insider's profit gets; and (3) When the volume of mimicking transaction is large and the private information is not much valuable, the likelihood of loss is high. We also validate certain theoretical results of our model using publicized ownership change data of major shareholders. As a result, we find the strategic evidences in the sample of insider transactions closing within 15 trading days. Also, although mimicking traders' losses have not been reported, they can suffer losses when the private information is not much valuable and the insiders take a significant strategic action. [source] | |||||||||||||