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The optimality model is a tool used to evaluate the effects of costs and benefits on animal behavior in the natural world. This evaluation allows researchers to make predictions about an animal’s optimal behavior. Optimality modeling is the modeling aspect of optimization theory. It allows for the visualization of the costs and benefits that influence the outcome of a decision and contributes to an understanding of animal adaptations. Optimal behavior is defined as an action that maximizes the difference between the costs and benefits of that decision. Three primary variables are used in the optimality model: decisions, currency, and constraints.〔Lucas, J. (1983). The role of foraging time constraints and variable prey encounter in optimal diet choice. The American Naturalist, 122(2), 191-209.〕 Decision involves evolutionary considerations of the costs and benefits of their actions. Currency is defined as the variable that is intended to be maximized (ex. food per unit of energy expenditure). It is the driving factor behind an action and usually involves food or other items essential to an animal’s survival. Constraints refer to the limitations placed on behavior, such as time and energy used to conduct that behavior. Optimality models are used to predict optimal behavior (ex. time spent foraging). To make predictions about optimal behavior, cost-benefit graphs are used to visualize the optimality model (see Fig 1). Optimality occurs at the point in which the difference between benefits and costs for obtaining a currency via a particular behavior is maximized. ==Constructing the Optimality Model== To construct an optimality model, the behavior must first be clearly defined. Then, descriptions of how the costs and benefits vary with the way the behavior is performed must be obtained.〔Parker, G., & Smith, J. (1990). Optimality theory in evolutionary biology. Nature, 348.〕 Examples of benefits and costs include direct fitness measures like offspring produced, change in lifespan, time spent or gained, or energy spent and gained. Each time an animal displays a certain behavior, it must weigh the costs and benefits to make a decision. For example, given X amount of time traveling, after catching one bug, would it be better for a bird to continue foraging or to quickly return to its nest to feed chicks? 〔Davies, N., Krebs, J., & West, S. (2012). Introduction to behavioural ecology. (4 ed.). Hoboken, NJ: John Wiley & Sons.〕 Better understanding of the relationships between the values in a model leads to better predictions of animal behavior. To determine the optimum time spent on a behavior, one can make a graph showing how benefits and costs change with behavior. Optimality is defined as the point where the difference between benefits and costs for a behavior is maximized, which can be done by graphing the benefits and costs on the y-axis and a measure of the behavior on the x-axis. A currency must also be identified. A test of the predictions generated by the optimality model can be performed to determine which currency the animal maximizes at any given time. For example, when constructing an optimality model for bee foraging time, researchers looked at whether energetic efficiency(energy gained/energy spent) or net rate of gain ((energy gained - energy spent)/time) was optimized. It was found that the bees maximized energetic efficiency when foraging for nectar.〔Schmid-Hempel, P. (1987). Efficient nectar-collecting by honeybees i. economic models. Journal of Animal Ecology, 56(1), 209-218. Retrieved from http://www.tb1.ethz.ch/PublicationsEO/PDFpapers/SCHMIDHEMPEL_JOURNAL_OF_ANIMAL_ECOLOGY_1987_56_209-218.pdf〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「optimality model」の詳細全文を読む スポンサード リンク
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