Individual Decision Making (individual + decision_making)

Distribution by Scientific Domains

Selected Abstracts

On the different nature of top-down and bottom-up effects in pelagic food webs

Z. Maciej Gliwicz
SUMMARY 1.,Each individual planktonic plant or animal is exposed to the hazards of starvation and risk of predation, and each planktonic population is under the control of resource limitation from the bottom up (growth and reproduction) and by predation from the top down (mortality). While the bottom-up and top-down impacts are traditionally conceived as compatible with each other, field population-density data on two coexisting Daphnia species suggest that the nature of the two impacts is different. Rates of change, such as the rate of individual body growth, rate of reproduction, and each species' population growth rate, are controlled from the bottom up. State variables, such as biomass, individual body size and population density, are controlled from the top down and are fixed at a specific level regardless of the rate at which they are produced. 2.,According to the theory of functional responses, carnivorous and herbivorous predators react to prey density rather than to the rate at which prey are produced or reproduced. The predator's feeding rate (and thus the magnitude of its effect on prey density) should hence be regarded as a functional response to increasing resource concentration. 3.,The disparity between the bottom-up and top-down effects is also apparent in individual decision making, where a choice must be made between accepting the hazards of hunger and the risks of predation (lost calories versus loss of life). 4.,As long as top-down forces are effective, the disparity with bottom-up effects seems evident. In the absence of predation, however, all efforts of an individual become subordinate to the competition for resources. Biomass becomes limited from the bottom up as soon as the density of a superior competitor has increased to the carrying capacity of a given habitat. Such a shift in the importance of bottom-up control can be seen in zooplankton in habitats from which fish have been excluded. [source]

A systematic review on communicating with patients about evidence

Lyndal J Trevena MBBS (Hons) MPhilPH
Abstract Objective, To conduct a systematic search for (1) the effectiveness of evidence-based communication tools to increase patient understanding of evidence, (2) effective formats for representing probabilistic information and (3) effective strategies for eliciting patient preferences about evidence. A case scenario is used to illustrate some of the difficulties of putting these results into practice., ,Data sources, Systematic search of The Cochrane Library, Medline, Psychinfo, Embase and Cancerlit. Review methods, Systematic reviews of randomized controlled trials (RCTs) and high quality RCTs were included. Studies were excluded if they did not address the question, were focused on behavioural outcomes without attempting to increase understanding, were concerned with counselling as a therapeutic intervention, or were specific to communication regarding clinical trial participation., ,Results, We found 10 systematic reviews of RCTs and 30 additional RCTs addressing our questions. Communication tools in most formats (verbal, written, video, provider-delivered, computer-based) will increase patients' understanding but are more likely to do so if structured, tailored and/or interactive. Probabilistic information is best represented as event rates (natural frequencies) in relevant groups of people, rather than words, probabilities or summarized as effect measures such as relative risk reduction. Illustrations such as cartoons, or graphs (vertical bar charts) appear to aid understanding. Values clarification exercises may be better than standard utility techniques for eliciting preferences in individual decision making. Looking for effective evidence-based communication tools for prostatic specific antigen testing highlighted the challenges for clinicians and consumers in accessing tools that are evidence-based in design as well as content. Conclusion, There is an increasing body of evidence supporting the design of effective evidence-based communication tools but variable access to such tools in practice. [source]


Marcello Basili
ABSTRACT The paper discusses the role of George L.S. Shackle in fostering an unconventional approach to individual decision making. Up until the early 1970s Shackle was the single critic of the probabilistic approach to decision making who proposed an alternative formal corpus for dealing with uncertainty. The main aim of the paper is to analyse Shackle's non-probabilistic conceptualization of individual decisions under uncertainty from a specific viewpoint, namely that of a possible connection between his theory and one of the most interesting recent approaches to decision under uncertainty, the so-called non-additive probability approach of Gilboa and Schmeidler. The paper shows that these developments in modern decision theory take Shackle's issue seriously and confirm that the reliance of strict Bayesian theory on probabilistic judgements based on point-probability estimates, a reliance that Shackle intended to oppose, is untenable. Non-additive decision theory also provides a usage of non-additive probability distributions in choice that is an alternative to Shackle's approach of using a qualitative notion of probability, such as potential surprise. [source]

Evaluation Periods and Asset Prices in a Market Experiment

Uri Gneezy
We test whether the frequency of feedback information about the performance of an investment portfolio and the flexibility with which the investor can change the portfolio influence her risk attitude in markets. In line with the prediction of myopic loss aversion (Benartzi and Thaler (1995)), we find that more information and more flexibility result in less risk taking. Market prices of risky assets are significantly higher if feedback frequency and decision flexibility are reduced. This result supports the findings from individual decision making, and shows that market interactions do not eliminate such behavior or its consequences for prices. [source]