The price of anarchy in social dilemmas: Traditional research paradigms and new network applications

Research on social dilemmas has largely been concerned with whether, and under what conditions, selfish decisions by autonomous individuals jointly result in socially inefficient outcomes. By contrast, considerably less emphasis has been placed on the extent of the inefficiency in those outcomes relative to the social optimum, and how the extent of inefficiency in theory compares with what is observed in experiments or practice. In this expository article, we introduce and subsequently extend the price of anarchy (PoA), an index that originated in studies on communication in computer science, and illustrate how it can be used to characterize the extent of inefficiency in social dilemmas. A second purpose of our article is to introduce a class of social dilemmas that occur when individuals selfishly choose routes in networks, and illustrate how the concept of PoA can be helpful in studying them.     

Adjustment to War Captivity: The Role of Sociodemographic Background,Trauma Severity,and Immediate Responses,in the Long-Term Mental Health of Israeli Ex-Pows

This study assessed the role of sociodemographic features, pre-captivity combat exposure, captivity severity, emotional responses and coping during captivity, and social support at homecoming, to the short- and long-term mental health of 164 Israeli POWs of the 1973 Yom Kippur War. The major contributors to the POWs' mental health were psychological responses during captivity, followed first by their education and ethnic status, and then by severity of captivity. Both traumatic stress of captivity and the results of the study were discussed in the light of Conservation of Resources (COR) theory.     

Variability in payoff disbursement in coalition formation experiments

Results from 680 plays, gathered in four different 3-person characteristic function game experiments, are summarized to show that there is considerable inter-group variability in payoff disbursement in coalition formation experiments that does not decrease with practice. This Variability is inconsistent with models predicting unique payoff vectors, one for each coalition structure. Data from a 3-person game experiment by Komorita and Kravitz are then employed to test and corroborate a recently proposed model, which predicts a range of payoff vectors in which each point depends on a single parameter interpretable as a standard of fairness.     

Computer controlled research on bargaining and coalition formation

Described in this paper is a research paradigm, written as a set of computer programs, to conduct on-line bargaining and coalition formation experiments within the characteristic function game framework. The structure of the paradigm is outlined, an example is presented and discussed, and further extensions of the program are briefly discussed.     

When three is not always two against one: Coalitions in experimental three-person cooperative games

Four models of coalition formation are tested in a computer-controlled experiment in which three players negotiated to form coalitions in order to gain rewards for themselves. Formation of the grand coalition of all three players as well as any of the three possible 2-person coalitions is permitted. The results indicate that the grand coalition is the most likely to form, followed by the coalition between the two strongest players. The individually rational bargaining set model of coalition formation is supported over an egalitarian model, the Shapley value, and the coalitionally rational bargaining set model. Various measures of the progress of negotiations are introduced, examined, and discussed in an effort to provide an increased data base for the establishment of a behavioral theory of bargaining and coalition formation.     

Attachment and psychological adaptation in high exposure survivors of the September 11th attack on the World Trade Center

This study examined the relationship between individual differences in adult attachment and psychological adaptation in a sample of high-exposure survivors of the terrorist attacks on the World Trade Center on September 11, 2001. Symptoms of posttraumatic stress disorder (PTSD) and depression were assessed via self-report 7 and 18 months after the attacks. In addition, friends and relatives were asked to provide evaluations of participants' adjustment before and after the attacks. Findings indicate that securely attached individuals exhibited fewer symptoms of PTSD and depression than insecurely attached individuals and were viewed by friends and relatives as showing an increase in adjustment following the attacks. Highly dismissing adults were viewed by their friends and family as showing neither increments nor decrements in adjustment, despite the fact that highly dismissing people self-reported relatively high levels of PTSD and depression.     

Strategic behavior in monkeys

In a recent paper, Lee et al. examined adaptive decision-making processes by training monkeys to play a competitive game against a computer programmed to play using various strategies. They found that the monkeys' responses were sensitive to the computer's strategies and consistent with reinforcement learning. Research such as this strongly complements current research in behavioral economics. We propose some potential future directions for this work, and put forward conjectures about what might be learned about decision-making in humans.     

Effects of observation cost on sequential search behavior

Sixty Ss participated individually in a search problem attempting to find a single target object located in one of several distinguishable regions. The search consisted of sampling observations with replacement from the various regions. Ss were told the prior probability of finding the target in a given region, the conditional miss probability that if the target is in a given region it will not be detected on a single observation there, and the cost per observation for each region. The effect of observation costs was investigated. Procedures devised for comparing actual and optimal search behavior showed that relative to the optimal policy Ss erred in the direction of maximizing detection probabilities rather than in the direction of minimizing the cost per observation, and that this error increased in magnitude the larger the differences among observation costs. A Markov model was tested and rejected. Implications of the study to visual search problems are discussed briefly.