Unlike infrastructure-based networks, mobile ad hoc networks consist of nodes independent of any infrastructure. Cooperation among these nodes is essential for the sustenance of multi hop communication. However, battery and bandwidth constraints may lead nodes in an ad hoc network to adopt energy- and bandwidth-conserving strategies. As routing and packet forwarding are end results of cooperation, network performance is affected when nodes in the network behave selfishly to conserve their resources. Our work involves characterizing selfish behavior by nodes in ad hoc networks and assessing the effectiveness of adopting tit for tat based strategies, which are meant to discourage selfish behavior in the network. We show that in an ad hoc network where other nodes act selfishly to conserve their resources, a node can benefit by adopting a generous tit for tat strategy. We also show that a node can gain benefit by avoiding selfish nodes in an ad hoc network, adopting a strategy that we call generous tit for tat with selfish avoidance (GTFT-SA) To analyze the effectiveness of cooperation strategies in selfish ad hoc networks we create an emulation environment based on virtualization. Such an emulation environment is more flexible to changes and is simpler to replicate than real life testbeds, while providing higher fidelity than simulations. / Master of Science

In Axelrod's tournaments of the Prisoner's Dilemma, carried out in the 1980s, a strategy called Tit for Tat was declared the winner, and it has since then been thought of as the strategy to use to do as well as possible in different situations. In this thesis, we investigate whether Tit for Tat will still do as well if we change the game to the Hawk-Dove Game. This is done by comparing Tit for Tat to other strategies -- All C, All D, Joss and Random -- one at a time. First we analyse under which conditions each strategy will be an Evolutionary Stable Strategy, then if it is possible for a population of these two strategies to end up in a stable polymorphism, and finally, if we have a finite population instead of an infinite one, under which conditions selection will favour the fixation of each of the strategies. This leads to the conclusion that how well Tit for Tat will do depends a lot on the different conditions on the game, but in general, the more times that a pair of individuals will meet, and the higher the value of the resource is compared to the cost of fighting, the better Tit for Tat will do.

Recently, the American Association of State Highway and Transportation Officials (AASHTO) indicated lack of competition and single-bid contracts in asphalt paving as a major issue facing state transportation departments. Single-bid contracts indicate a lack of competition which increases costs to state and local governments. During the period from 2005-2007 in Kentucky, 42 percent of all bids were awarded with only one firm bidding on the project. Of the asphalt paving jobs, 63 percent of those jobs were awarded to a single bidder. The analysis of this dissertation focuses on detecting tacit collusion in asphalt paving jobs in Kentucky. A focal point enables firms to coordinate bids and engage in a tit-for-tat strategy where they refuse to bid in each other’s counties. In this case the focal point is the county boundaries. Two factors contribute to the ability of firms to use county boundaries to coordinate bids. The first factor is that the political county boundaries form relatively small counties which allow a firm’s service area to cover multiple counties. The firms are able to claim counties and service the projects in those counties. The second factor is that a majority of asphalt projects which the Kentucky Transportation Cabinet puts up for bidding are exclusive to a specific county. This allows firms to know whether a project falls in a county within their bidding territory. Each county and firm in each of the 12 Kentucky Transportation Cabinet geographic districts was analyzed to see if there was evidence of bid coordination. The result is that in 94 out of 120 counties there was evidence of bid coordination or tacit collusion with increases in bid levels. There is evidence that 25 of the 31 Kentucky asphalt paving firms refuse to bid against their rivals in their rival’s territories. This refusal by firms to bid against each other resulted in single-bid contracts that were $70,595,466.09 above the competitive level.

Au niveau interpersonnel, la psychopathie implique un manque de considération d’autrui pouvant se manifester par la tromperie, la manipulation et l’exploitation. La présente thèse a investigué la relation entre les caractéristiques psychopathiques d'individus non incarcérés et la tendance à coopérer dans un jeu du dilemme du prisonnier itératif. Un total de 85 hommes ont été recrutés via une annonce qui ciblait des traits de personnalité correspondant à des caractéristiques psychopathiques exprimées de façon non péjorative. Plusieurs méthodes ont été employées pour rejoindre les participants : 46 ont participés en personne après avoir répondu à une invitation affichée dans un journal local ainsi que sur des babillards à proximité d'une université; 39 ont complété l'étude sur Internet après avoir été recrutés via un site web de petites annonces. Chaque participant a répondu à un questionnaire incluant l’Échelle Auto-rapportée de Psychopathie (Levenson, Kiehl, & Fitzpatrick, 1995) et l’Échelle Auto-rapportée des Indicateurs de Psychopathie de l’Enfance et de l’Adolescence (Seto, Khattar, Lalumière, & Quinsey, 1997). Ils ont également complété une simulation informatique du dilemme du prisonnier itératif comprenant 90 essais. La simulation informatique utilisée pour évaluer les participants en personne ainsi que la version accessible par Internet ont été conçues et programmées spécifiquement pour la présente thèse. La simulation informatique incluait trois stratégies souvent associées au dilemme du prisonnier itératif : donnant-donnant, donnant-donnant-généreux et gagne/reste-perd/change. Les analyses préliminaires ont montré que les participants vus en personne et ceux rejoints par Internet ne différaient pas en termes de variables sociodémographiques, des caractéristiques psychopathiques, de la désirabilité sociale et des réponses au dilemme du prisonnier. Une régression multiple standard a indiqué que les mesures psychopathiques ne pouvaient pas prédire le nombre total de choix coopératifs dans le jeu. Par contre, une corrélation négative a été trouvée entre les caractéristiques interpersonnelles et affectives de la psychopathie et la coopération dans le premier tiers du jeu. De plus, les participants qui présentaient davantage de caractéristiques psychopathiques interpersonnelles et affectives avaient plus souvent réussi à exploiter l'ordinateur en dénonçant alors que la simulation informatique coopérait. Des analyses multi-niveaux ont exploré la contribution de variables au niveau de la décision et au niveau de l'individu dans la prédiction du choix de coopérer ou de dénoncer lors de chaque essai du jeu; les interactions entre ces variables ont aussi été considérées. Les résultats ont montré que les variables au niveau de la décision influençaient généralement plus fortement les chances de coopérer que les variables au niveau de l'individu. Parmi les mesures de la psychopathie, seulement les caractéristiques interpersonnelles et affectives ont montré une association significative avec les chances de coopérer; les interactions avec le premier choix effectué dans le jeu et le premier tiers du jeu étaient significatives. Ainsi, si un participant avait coopéré au premier essai, la présence de caractéristiques psychopathiques interpersonnelles et affectives était associée à une diminution de ses chances de coopérer par la suite. Aussi, durant les 30 premiers essais du jeu, la présence de caractéristiques psychopathiques interpersonnelles et affectives était associée à une diminution des chances de coopérer. La stratégie adoptée par la simulation informatique n'avait pas d'influence sur le lien entre les caractéristiques psychopathiques et la probabilité de coopérer. Toutefois, le fait de jouer contre donnant-donnant était associé à de plus fortes chances de coopérer d'un essai à l'autre pour l'ensemble des participants. Globalement, les résultats suggèrent que les hommes non incarcérés présentant des caractéristiques psychopathiques ne seraient pas nécessairement portés à choisir systématiquement la non-coopération. En fait, les caractéristiques interpersonnelles et affectives de la psychopathie ont semblé se traduire par une tendance à faire bonne impression au départ, tenter rapidement d'exploiter autrui en dénonçant, puis finir par coopérer. Cette tendance comportementale est discutée, ainsi que la pertinence d'utiliser le dilemme du prisonnier itératif et les analyses multi-niveaux pour étudier le comportement interpersonnel des psychopathes. / Interpersonally, psychopathy involves a lack of consideration for others that can translate into deception, manipulation, and exploitation. The current thesis investigated the relationship between the psychopathic characteristics of non incarcerated men and the tendency to cooperate while playing an iterative version of the prisoner's dilemma game. A total of 85 men were recruited through advertisements that targeted personality traits corresponding to psychopathic characteristics formulated in a way that was not pejorative. A variety of methods was used to reach participants; 46 were tested in person after they replied to an invitation that appeared in a local journal as well as on bulletin boards close to a university; 39 participated via the Internet after they were recruited through a classified advertising website. Each participant completed a questionnaire including the Levenson Self-Report Psychopathy Scale (Levenson, Kiehl, & Fitzpatrick, 1995) and the Childhood and Adolescent Taxon Scale - Self-Report (Seto, Khattar, Lalumière, & Quinsey, 1997). They also played in a computer simulation of the iterative prisoner's dilemma lasting 90 trials. Both the computer simulation used to test participants in person and the Internet version were designed and programmed specifically for the present thesis. The computer simulation included three strategies often associated with the iterative prisoner's dilemma: tit-for-tat, generous-tit-for-tat, and win/stay-lose/shift. Preliminary analyses showed that participants tested in person and via the Internet did not differ in terms of sociodemographic variables, psychopathic characteristics, social desirability, or responses to the prisoner's dilemma. A standard multiple regression indicated that psychopathic measures could not predict the total number of cooperative choices in the prisoner's dilemma game. However, there was a negative correlation between interpersonal and affective characteristics of psychopathy and cooperation in the first third of the prisoner's dilemma game. Furthermore, participants showing more interpersonal and affective psychopathic characteristics tended to exploit the computer more often by defecting while the computer simulation cooperated. Multilevel analyses were used to explore the contribution of decision-level and individual-level variables to predict the choice to cooperate or to defect on each trial of the game; interactions between these variables were also considered. The results showed that variables at the decision level were generally associated with stronger odds of cooperating than individual-level variables. Among psychopathic measures, only the interpersonal and affective characteristics showed a significant association with the odds of cooperating; interactions with the first choice in the game and the first third of the game were significant. That is, if participants cooperated in the first trial, higher interpersonal and affective psychopathic characteristics were associated with decreased odds of cooperating. Also, during the first 30 trials of the game, participants with higher interpersonal and affective psychopathic characteristics were significantly more likely to defect. The type of strategy used by the computer simulation did not have an influence on the relationship between psychopathic characteristics and a participant's probability to cooperate. However, playing against tit-for-tat was associated with increased odds of cooperating from one trial to the next for all participants. Overall, the results suggest that non incarcerated men with psychopathic characteristics might not systematically choose to defect. Instead, the interpersonal and affective psychopathic characteristics appeared as a tendency to cooperate initially, then rapidly attempt to exploit by defecting, and finally cooperate. This behavioral pattern is discussed as well as the relevance of using the iterative prisoner's dilemma game and multilevel analyses to study interpersonal behavior in psychopaths.

The present paper aims to show that the oligopoly problem is much more determined than commonly believed. In oligopoly prerequisites are likely to prevail inducing a 'normal' behaviour in accordance with profit maximization. This leads to a price combination located at an exactly definable line section. Finally some consequences upon economic policy are outlined. / Dieser Beitrag versucht zu zeigen, daß das Oligopolproblem wesentlich determinierter ist als gemeinhin angenommen. Im Oligopol liegen die Voraussetzungen besonders günstig, daß durch ein aus dem Streben nach Gewinnmaximierung abgeleitetes, "normales" Verhalten eine Preiskombination auf einem exakt abgrenzbaren Kurvenabschnitt zustande kommt. Abschließend werden wirtschaftspolitische Konsequenzen angedeutet.

The present paper aims to show that the oligopoly problem is much more determined than commonly believed. In oligopoly prerequisites are likely to prevail inducing a 'normal' behaviour in accordance with profit maximization. This leads to a price combination located at an exactly definable line section. Finally some consequences upon economic policy are outlined. / Dieser Beitrag versucht zu zeigen, daß das Oligopolproblem wesentlich determinierter ist als gemeinhin angenommen. Im Oligopol liegen die Voraussetzungen besonders günstig, daß durch ein aus dem Streben nach Gewinnmaximierung abgeleitetes, "normales" Verhalten eine Preiskombination auf einem exakt abgrenzbaren Kurvenabschnitt zustande kommt. Abschließend werden wirtschaftspolitische Konsequenzen angedeutet.