Prospect Theory and Limit Lines

Risk acceptance criteria in the form of limit lines are investigated in the context of prospect theory. This theory departs from utility theory in several respects, an important one being the use of weights other than probabilities in the evaluation of the expected impact of uncertain outcomes. Hypothetical functions reflecting certain attitudes toward consequences and rare events are developed and combined to produce several limit lines.     

Mitochondrial abnormalities and oxidative imbalance in neurodegenerative disease

An increasing body of evidence now suggests the involvement of mitochondrial abnormalities in the etiology of neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer disease. In this Perspective, we describe a recent study that shows that treatment of human patients with the antioxidant coenzyme Q(10'), which functions in concert with certain mitochondrial enzymes, reduced the worsening of symptoms associated with PD. These findings are consistent with the hypothesis that mitochondrial dysfunction plays a role in the pathogenesis of PD and that treatments that target mitochondrial biochemistry might ameliorate the functional decline observed in patients suffering from PD.     

An Empirical Test of the Relative Validity of Expert and Lay Judgments of Risk

This article investigates how accurately experts (underwriters) and lay persons (university students) judge the risks posed by life-threatening events Only one prior study (Slovic, Fischhoff, & Lichtenstein, 1985) has previously investigated the veracity of expert versus lay judgments of the magnitude of risk. In that study, a heterogeneous grouping of 15 experts was found to judge, using marginal estimations, a variety of risks as closer to the true annual frequencies of death than convenience samples of the lay population. In this study, we use a larger, homogenous sample of experts performing an ecologically valid task. We also ask our respondents to assess frequencies and relative frequencies directly, rather than ask for a "risk" estimate--a response mode subject to possible qualitative attributions-as was done in the Slovic et al. study. Although we find that the experts outperformed lay persons on a number of measures, the differences are small, and both groups showed similar global biases in terms of: (1) overestimating the likelihood of dying from a condition (marginal probability) and of dying from a condition given that it happens to you (conditional probability), and (2) underestimating the ratios of marginal and conditional likelihoods between pairs of potentially lethal events. In spite of these scaling problems, both groups showed quite good performance in ordering the lethal events in terms of marginal and conditional likelihoods. We discuss the nature of expertise using a framework developed by Bolger and Wright (1994), and consider whether the commonsense assumption of the superiority of expert risk assessors in making magnitude judgments of risk is, in fact, sensible.     

$7.8 Billion for Everglades Restoration: Why Do Environmentalists Look So Worried?

The Comprehensive Everglades Restoration Plan, enacted in 2000, is a $7.8 billion federal/state investment in restoring the Florida Everglades ecosystem. The plan is a negotiated compromise between divergent interests in south Florida and promises to provide water and flood control for urban and agricultural users while maintaining a priority commitment to the natural system when allocating water produced by the 30-year project. The environmental community calls for independent scientific review of un-tested technologies, early and substantial hydrologic benefits to the remaining Everglades, including Everglades National Park, and strong programmatic regulations of the federal project to ensure that ecological restoration remains its primary purpose in spite of inherently conflicting interests at the state and local level.     

It's a rave new world: estimating the prevalence and perceived harm of ecstasy and other drug use among club rave attendees

The use of 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") appears to be increasing worldwide, with "rave" attendees being one high-risk population. To date, however, only one study has collected ecstasy use information from rave attendees in the United States. To address this limitation, we collected self-report drug use information from 70 adult "club rave" attendees within the Baltimore-Washington corridor in April and May 2002. Data collection was scheduled between 12 A.M. and 5 A.M. Participation rates were high, with 85 percent of the club rave attendees completing the interview. Eighty-six percent of the respondents reported lifetime ecstasy use, 51 percent reported 30-day use, and 30 percent reported using ecstasy within the two days preceding the interview. While past-year ecstasy users were comparable to non-users with respect to a host of demographic and drug use variables, non-ecstasy users were significantly more likely than past-year users to perceive risks associated with the regular use of alcohol and ecstasy. Not surprisingly, non-ecstasy users were significantly more likely than past-year users to perceive harmful long-term physical and psychological effects associated with ecstasy ingestion. These findings suggest that rave attendees may be an important population for ecstasy-related prevention efforts.     

Beliefs and social norms about codeine and promethazine hydrochloride cough syrup (CPHCS) onset and perceived addiction among urban Houstonian adolescents: an addiction trend in the city of lean

In the current study, we used a qualitative approach to investigate relevant beliefs and norms associated with codeine and promethazine hydrochloride cough syrup (CPHCS) consumption, initiation, and perceived addiction among 48 alternative school students who identified themselves as current CPHCS users. In general, both boys and girls believed that CPHCS addiction started during an individual's initial consumption. A majority of both groups reported that their second CPHCS event was initiated during the same or next day after their first event. Our findings suggest that friends and an innovative form of hip-hop music called "screw" are strong reinforcers of CPHCS use.     

Medicines in the 1990's: Experience with a Delphi forecast

‘Medicines in the 1990's’ created great public interest when it was published recently. It forecast, for example, that by 1990 it should be possible to replace almost all parts of the body, except the brain and spinal cord with transplants or prostheses. It also predicted that by 1990, the social use of medicines will have become accepted as legitimate. This article describes step by step, how the Delphi forecast was made and the effect which it has had.     

A model for collaboration networks giving rise to a power-law distribution with an exponential cutoff

Recently several authors have proposed stochastic evolutionary models for the growth of complex networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the “rich get richer” phenomenon. Despite the generality of the proposed stochastic models, there are still some unexplained phenomena, which may arise due to the limited size of networks such as protein, e-mail, actor and collaboration networks. Such networks may in fact exhibit an exponential cutoff in the power-law scaling, although this cutoff may only be observable in the tail of the distribution for extremely large networks. We propose a modification of the basic stochastic evolutionary model, so that after a node is chosen preferentially, say according to the number of its inlinks, there is a small probability that this node will become inactive. We show that as a result of this modification, by viewing the stochastic process in terms of an urn transfer model, we obtain a power-law distribution with an exponential cutoff. Unlike many other models, the current model can capture instances where the exponent of the distribution is less than or equal to two. As a proof of concept, we demonstrate the consistency of our model empirically by analysing the Mathematical Research collaboration network, the distribution of which has been shown to be compatible with a power law with an exponential cutoff.