Simulit, un modèle de simulation pour la planification hospitalière. [Simulit, a simulation model for hospital planning].

The aim of this computerized simulation model is to provide an estimate of the number of beds used by a population, taking into accounts important determining factors. These factors are demographic data of the deserved population, hospitalization rates, hospital case-mix and length of stay; these parameters can be taken either from observed data or from scenarii. As an example, the projected evolution of the number of beds in Canton Vaud for the period 1893-2010 is presented.

The effect of learning on the evolution of new courtship behavior: a simulation model

The fact that individuals learn can change the relationship between genotype and phenotype in the population, and thus affect the evolutionary response to selection. Here we ask how male ability to learn from female response affects the evolution of a novel male behavioral courtship trait under pre-existing female preference (sensory drive). We assume a courtship trait which has both a genetic and a learned component, and a two-level female response to males. With individual-based simulations we show that, under this scenario, learning generally increases the strength of selection on the genetic component of the courtship trait, at least when the population genetic mean is still low. As a consequence, learning not only accelerates the evolution of the courtship trait, but also enables it when the trait is costly, which in the absence of learning results in an adaptive valley. Furthermore, learning can enable the evolution of the novel trait in the face of gene flow mediated by immigration of males that show superior attractiveness to females based on another, non-heritable trait. However, rather than increasing monotonically with the speed of learning, the effect of learning on evolution is maximized at intermediate learning rates. This model shows that, at least under some scenarios, the ability to learn can drive the evolution of mating behaviors through a process equivalent to Waddington's genetic assimilation.

Cell-based computational modeling of vascular morphogenesis using Tissue Simulation Toolkit.

Computational modeling has become a widely used tool for unraveling the mechanisms of higher level cooperative cell behavior during vascular morphogenesis. However, experimenting with published simulation models or adding new assumptions to those models can be daunting for novice and even for experienced computational scientists. Here, we present a step-by-step, practical tutorial for building cell-based simulations of vascular morphogenesis using the Tissue Simulation Toolkit (TST). The TST is a freely available, open-source C++ library for developing simulations with the two-dimensional cellular Potts model, a stochastic, agent-based framework to simulate collective cell behavior. We will show the basic use of the TST to simulate and experiment with published simulations of vascular network formation. Then, we will present step-by-step instructions and explanations for building a recent simulation model of tumor angiogenesis. Demonstrated mechanisms include cell-cell adhesion, chemotaxis, cell elongation, haptotaxis, and haptokinesis.

A deterministic model to assess the impact of AIDS interventions in countries with generalized HIV epidemic. An application to Botswana

General introductionThe Human Immunodeficiency/Acquired Immunodeficiency Syndrome (HIV/AIDS) epidemic, despite recent encouraging announcements by the World Health Organization (WHO) is still today one of the world's major health care challenges.The present work lies in the field of health care management, in particular, we aim to evaluate the behavioural and non-behavioural interventions against HIV/AIDS in developing countries through a deterministic simulation model, both in human and economic terms. We will focus on assessing the effectiveness of the antiretroviral therapies (ART) in heterosexual populations living in lesser developed countries where the epidemic has generalized (formerly defined by the WHO as type II countries). The model is calibrated using Botswana as a case study, however our model can be adapted to other countries with similar transmission dynamics.The first part of this thesis consists of reviewing the main mathematical concepts describing the transmission of infectious agents in general but with a focus on human immunodeficiency virus (HIV) transmission. We also review deterministic models assessing HIV interventions with a focus on models aimed at African countries. This review helps us to recognize the need for a generic model and allows us to define a typical structure of such a generic deterministic model.The second part describes the main feed-back loops underlying the dynamics of HIV transmission. These loops represent the foundation of our model. This part also provides a detailed description of the model, including the various infected and non-infected population groups, the type of sexual relationships, the infection matrices, important factors impacting HIV transmission such as condom use, other sexually transmitted diseases (STD) and male circumcision. We also included in the model a dynamic life expectancy calculator which, to our knowledge, is a unique feature allowing more realistic cost-efficiency calculations. Various intervention scenarios are evaluated using the model, each of them including ART in combination with other interventions, namely: circumcision, campaigns aimed at behavioral change (Abstain, Be faithful or use Condoms also named ABC campaigns), and treatment of other STD. A cost efficiency analysis (CEA) is performed for each scenario. The CEA consists of measuring the cost per disability-adjusted life year (DALY) averted. This part also describes the model calibration and validation, including a sensitivity analysis.The third part reports the results and discusses the model limitations. In particular, we argue that the combination of ART and ABC campaigns and ART and treatment of other STDs are the most cost-efficient interventions through 2020. The main model limitations include modeling the complexity of sexual relationships, omission of international migration and ignoring variability in infectiousness according to the AIDS stage.The fourth part reviews the major contributions of the thesis and discusses model generalizability and flexibility. Finally, we conclude that by selecting the adequate interventions mix, policy makers can significantly reduce the adult prevalence in Botswana in the coming twenty years providing the country and its donors can bear the cost involved.Part I: Context and literature reviewIn this section, after a brief introduction to the general literature we focus in section two on the key mathematical concepts describing the transmission of infectious agents in general with a focus on HIV transmission. Section three provides a description of HIV policy models, with a focus on deterministic models. This leads us in section four to envision the need for a generic deterministic HIV policy model and briefly describe the structure of such a generic model applicable to countries with generalized HIV/AIDS epidemic, also defined as pattern II countries by the WHO.

Impact de la prophylaxie hormonale sur les fractures du fémur proximal des femmes postménopausiques: une étude de simulation. [Impact of hormonal prevention on fractures of the proximal femur in postmenopausal women: a simulation study].

A simulation model of the effects of hormone replacement therapy (HRT) on hip fractures and their consequences is based on a population of 100,000 post-menopausal women. This cohort is confronted with literature derived probabilities of cancers (endometrium or breast, which are contra-indications to HRT), hip fracture, disability requiring nursing home or home care, and death. Administration of HRT for life prevents 55,5% of hip fractures, 22,6% of years with home care and 4,4% of years in nursing homes. If HRT is administered for 15 years, these results are 15,5%, 10% and 2,2%, respectively. A slight gain in life expectancy is observed for both durations of HRT. The net financial loss in the simulated population is 222 million Swiss Francs (cost/benefit ratio 1.25) for lifelong administration of HRT, and 153 million Swiss Francs (cost/benefit ratio 1.42) if HRT is administered during 15 years.

Using robots to understand social behaviour.

A major challenge in studying social behaviour stems from the need to disentangle the behaviour of each individual from the resulting collective. One way to overcome this problem is to construct a model of the behaviour of an individual, and observe whether combining many such individuals leads to the predicted outcome. This can be achieved by using robots. In this review we discuss the strengths and weaknesses of such an approach for studies of social behaviour. We find that robots-whether studied in groups of simulated or physical robots, or used to infiltrate and manipulate groups of living organisms-have important advantages over conventional individual-based models and have contributed greatly to the study of social behaviour. In particular, robots have increased our understanding of self-organization and the evolution of cooperative behaviour and communication. However, the resulting findings have not had the desired impact on the biological community. We suggest reasons for why this may be the case, and how the benefits of using robots can be maximized in future research on social behaviour.

Evaluation of an online, case-based interactive approach to teaching pathophysiology

Rapport de synthèse : L'article qui fait l'objet de ma thèse évalue une nouvelle approche pédagogique pour l'apprentissage de certains chapitres de physiopathologie. Le dispositif pédagogique se base sur l'alternance d'apprentissage ex-cathedra et de l'utilisation d'un site web comprenant des vignettes cliniques. Lors de la consultation de ces-dernières, l'étudiant est invité à demander des examens de laboratoire dont il pourrait justifier la pertinence selon le cas clinique étudié. La nouveauté du procédé réside dans le fait que, préalablement à son cours ex-cathedra, l'enseignant peut consulter les statistiques de demandes de laboratoire et ainsi orienter son cours selon les éléments mal compris par les étudiants. A la suite du cours ex-cathedra, les étudiants peuvent consulter sur internet la vignette clinique complète avec des explications. A l'issue de tout le cours, une évaluation auprès des étudiants a été conduite. Le procédé a été mis en place durant deux années consécutives et l'article en discute notamment les résultats. Nous avons pu conclure que cette méthode innovatrice d'enseignement amène les étudiants à mieux se préparer pour les cours ex-cathedra tout en permettant à l'enseignant d'identifier plus précisément quelles thématiques étaient difficiles pour les étudiants et donc d'ajuster au mieux son cours. Mon travail de thèse a consisté à créer ce dispositif d'apprentissage, à créer l'application web des vignettes cliniques et à l'implanter durant deux années consécutives. J'ai ensuite analysé les données des évaluations et écrit l'article que j'ai présenté à la revue 'Medical Teacher'. Après quelques corrections et précisions demandées par le comité de lecture, l'article a été accepté et publié. Ce travail a débouché sur une seconde version de l'application web qui est actuellement utilisée lors du module 3.1 de 3è année à l'Ecole de Médecine à Lausanne. Summary : Since the early days of sexual selection, our understanding of the selective forces acting on males and females during reproduction has increased remarkably. However, despite a long tradition of experimental and theoretical work in this field and relentless effort, numerous questions remain unanswered and many results are conflicting. Moreover, the interface between sexual selection and conservation biology has to date received little attention, despite existing evidence for its importance. In the present thesis, I first used an empirical approach to test various sexual selection hypotheses in a population of whitefish of central Switzerland. This precise population is characterized by a high prevalence of gonadal alterations in males. In particular, I challenged the hypothesis that whitefish males displaying peculiar gonadal features are of lower genetic quality than other seemingly normal males. Additionally, I also worked on identifying important determinant of sperm behavior. During a second theoretical part of my work, which is part of a larger project on the evolution of female mate preferences in harvested fish populations, I developed an individual-based simulation model to estimate how different mate discrimination costs affect the demographical behavior of fish populations and the evolutionary trajectories of female mate preferences. This latter work provided me with some insight on a recently published article addressing the importance of sexual selection for harvesting-induced evolution. I built upon this insight in a short perspective paper. In parallel, I let some methodological questions drive my thoughts, and wrote an essay about possible synergies between the biological, the philosophical and the statistical approach to biological questions.

Homeostatic and circadian contribution to EEG and molecular state variables of sleep regulation.

STUDY OBJECTIVES: Besides their well-established role in circadian rhythms, our findings that the forebrain expression of the clock-genes Per2 and Dbp increases and decreases, respectively, in relation to time spent awake suggest they also play a role in the homeostatic aspect of sleep regulation. Here, we determined whether time of day modulates the effects of elevated sleep pressure on clock-gene expression. Time of day effects were assessed also for recognized electrophysiological (EEG delta power) and molecular (Homer1a) markers of sleep homeostasis. DESIGN: EEG and qPCR data were obtained for baseline and recovery from 6-h sleep deprivation starting at ZT0, -6, -12, or -18. SETTING: Mouse sleep laboratory. PARTICIPANTS: Male mice. INTERVENTIONS: Sleep deprivation. RESULTS: The sleep-deprivation induced changes in Per2 and Dbp expression importantly varied with time of day, such that Per2 could even decrease during sleep deprivations occurring at the decreasing phase in baseline. Dbp showed similar, albeit opposite dynamics. These unexpected results could be reliably predicted assuming that these transcripts behave according to a driven damped harmonic oscillator. As expected, the sleep-wake distribution accounted for a large degree of the changes in EEG delta power and Homer1a. Nevertheless, the sleep deprivation-induced increase in delta power varied also with time of day with higher than expected levels when recovery sleep started at dark onset. CONCLUSIONS: Per2 and delta power are widely used as exclusive state variables of the circadian and homeostatic process, respectively. Our findings demonstrate a considerable cross-talk between these two processes. As Per2 in the brain responds to both sleep loss and time of day, this molecule is well positioned to keep track of and to anticipate homeostatic sleep need. CITATION: Curie T; Mongrain V; Dorsaz S; Mang GM; Emmenegger Y; Franken P. Homeostatic and circadian contribution to EEG and molecular state variables of sleep regulation. SLEEP 2013;36(3):311-323.

Transition to parenthood: The role of social interaction and endogenous networks

Empirical studies indicate that the transition to parenthood is influenced by an individual's peer group. To study the mechanisms creating interdepen- dencies across individuals' transition to parenthood and its timing we apply an agent-based simulation model. We build a one-sex model and provide agents with three different characteristics regarding age, intended education and parity. Agents endogenously form their network based on social closeness. Network members then may influence the agents' transition to higher parity levels. Our numerical simulations indicate that accounting for social inter- actions can explain the shift of first-birth probabilities in Austria over the period 1984 to 2004. Moreover, we apply our model to forecast age-specific fertility rates up to 2016.

Cost-effectiveness analysis of a European primary-care physician training in smoking cessation counseling.

BACKGROUND: Physician training in smoking cessation counseling has been shown to be effective as a means to increase quit success. We assessed the cost-effectiveness ratio of a smoking cessation counseling training programme. Its effectiveness was previously demonstrated in a cluster randomized, control trial performed in two Swiss university outpatients clinics, in which residents were randomized to receive training in smoking interventions or a control educational intervention. DESIGN AND METHODS: We used a Markov simulation model for effectiveness analysis. This model incorporates the intervention efficacy, the natural quit rate, and the lifetime probability of relapse after 1-year abstinence. We used previously published results in addition to hospital service and outpatient clinic cost data. The time horizon was 1 year, and we opted for a third-party payer perspective. RESULTS: The incremental cost of the intervention amounted to US$2.58 per consultation by a smoker, translating into a cost per life-year saved of US$25.4 for men and 35.2 for women. One-way sensitivity analyses yielded a range of US$4.0-107.1 in men and US$9.7-148.6 in women. Variations in the quit rate of the control intervention, the length of training effectiveness, and the discount rate yielded moderately large effects on the outcome. Variations in the natural cessation rate, the lifetime probability of relapse, the cost of physician training, the counseling time, the cost per hour of physician time, and the cost of the booklets had little effect on the cost-effectiveness ratio. CONCLUSIONS: Training residents in smoking cessation counseling is a very cost-effective intervention and may be more efficient than currently accepted tobacco control interventions.

Invasion and eradication of a competitively superior species in heterogeneous landscapes

The effect of heterogeneous environments upon the dynamics of invasion and the eradication or control of invasive species is poorly understood, although it is a major challenge for biodiversity conservation. Here, we first investigate how the probability and time for invasion are affected by spatial heterogeneity. Then, we study the effect of control program strategies (e.g. species specificity, spatial scale of action, detection and eradication efficiency) on the success and time of eradication. We find that heterogeneity increases both the invasion probability and the time to invasion. Heterogeneity also reduces the probability of eradication but does not change the time taken for successful eradication. We confirm that early detection of invasive species reduces the time until eradication, but we also demonstrate that this is true only if the local control action is sufficiently efficient. The criterion of removal efficiency is even more important for an eradication program than simply ensuring control effort when the invasive species is not abundant.

Does colonization asymmetry matter in metapopulations?

Despite the considerable evidence showing that dispersal between habitat patches is often asymmetric, most of the metapopulation models assume symmetric dispersal. In this paper, we develop a Monte Carlo simulation model to quantify the effect of asymmetric dispersal on metapopulation persistence. Our results suggest that metapopulation extinctions are more likely when dispersal is asymmetric. Metapopulation viability in systems with symmetric dispersal mirrors results from a mean field approximation, where the system persists if the expected per patch colonization probability exceeds the expected per patch local extinction rate. For asymmetric cases, the mean field approximation underestimates the number of patches necessary for maintaining population persistence. If we use a model assuming symmetric dispersal when dispersal is actually asymmetric, the estimation of metapopulation persistence is wrong in more than 50% of the cases. Metapopulation viability depends on patch connectivity in symmetric systems, whereas in the asymmetric case the number of patches is more important. These results have important implications for managing spatially structured populations, when asymmetric dispersal may occur. Future metapopulation models should account for asymmetric dispersal, while empirical work is needed to quantify the patterns and the consequences of asymmetric dispersal in natural metapopulations.

Interacting populations in heterogeneous environments

To optimally manage a metapopulation, managers and conservation biologists can favor a type of habitat spatial distribution (e.g. aggregated or random). However, the spatial distribution that provides the highest habitat occupancy remains ambiguous and numerous contradictory results exist. Habitat occupancy depends on the balance between local extinction and colonization. Thus, the issue becomes even more puzzling when various forms of relationships - positive or negative co-variation - between local extinction and colonization rate within habitat types exist. Using an analytical model we demonstrate first that the habitat occupancy of a metapopulation is significantly affected by the presence of habitat types that display different extinction-colonization dynamics, considering: (i) variation in extinction or colonization rate and (ii) positive and negative co-variation between the two processes within habitat types. We consequently examine, with a spatially explicit stochastic simulation model, how different degrees of habitat aggregation affect occupancy predictions under similar scenarios. An aggregated distribution of habitat types provides the highest habitat occupancy when local extinction risk is spatially heterogeneous and high in some places, while a random distribution of habitat provides the highest habitat occupancy when colonization rates are high. Because spatial variability in local extinction rates always favors aggregation of habitats, we only need to know about spatial variability in colonization rates to determine whether aggregating habitat types increases, or not, metapopulation occupancy. From a comparison of the results obtained with the analytical and with the spatial-explicit stochastic simulation model we determine the conditions under which a simple metapopulation model closely matches the results of a more complex spatial simulation model with explicit heterogeneity.

Generation and interconnection capacity expansion in cross-border electricity markets : the need for policy coordination

Electricity is a strategic service in modern societies. Thus, it is extremely important for governments to be able to guarantee an affordable and reliable supply, which depends to a great extent on an adequate expansion of the generation and transmission capacities. Cross- border integration of electricity markets creates new challenges for the regulators, since the evolution of the market is now influenced by the characteristics and policies of neighbouring countries. There is still no agreement on why and how regions should integrate their electricity markets. The aim of this thesis is to improve the understanding of integrated electricity markets and how their behaviour depends on the prevailing characteristics of the national markets and the policies implemented in each country. We developed a simulation model to analyse under what circumstances integration is desirable. This model is used to study three cases of interconnection between two countries. Several policies regarding interconnection expansion and operation, combined with different generation capacity adequacy mechanisms, are evaluated. The thesis is composed of three papers. The first paper presents a detailed description of the model and an analysis of the case of Colombia and Ecuador. It shows that market coupling can bring important benefits, but the relative size of the countries can lead to import dependency issues in the smaller country. The second paper compares the case of Colombia and Ecuador with the case of Great Britain and France. These countries are significantly different in terms of electricity sources, hydro- storage capacity, complementarity and demand growth. We show that complementarity is essential in order to obtain benefits from integration, while higher demand growth and hydro- storage capacity can lead to counterintuitive outcomes, thus complicating policy design. In the third paper, an extended version of the model presented in the first paper is used to analyse the case of Finland and its interconnection with Russia. Different trading arrangements are considered. We conclude that unless interconnection capacity is expanded, the current trading arrangement, where a single trader owns the transmission rights and limits the flow during peak hours, is beneficial for Finland. In case of interconnection expansion, market coupling would be preferable. We also show that the costs of maintaining a strategic reserve in Finland are justified in order to limit import dependency, while still reaping the benefits of interconnection. In general, we conclude that electricity market integration can bring benefits if the right policies are implemented. However, a large interconnection capacity is only desirable if the countries exhibit significant complementarity and trust each other. The outcomes of policies aimed at guaranteeing security of supply at a national level can be quite counterintuitive due to the interactions between neighbouring countries and their effects on interconnection and generation investments. Thus, it is important for regulators to understand these interactions and coordinate their decisions in order to take advantage of the interconnection without putting security of supply at risk. But it must be taken into account that even when integration brings benefits to the region, some market participants lose and might try to hinder the integration process. -- Dans les sociétés modernes, l'électricité est un service stratégique. Il est donc extrêmement important pour les gouvernements de pouvoir garantir la sécurité d'approvisionnement à des prix abordables. Ceci dépend en grande mesure d'une expansion adéquate des capacités de génération et de transmission. L'intégration des marchés électriques pose des nouveaux défis pour les régulateurs, puisque l'évolution du marché est maintenant influencée par les caractéristiques et les politiques des pays voisins. Il n'est pas encore claire pourquoi ni comment les marches électriques devraient s'intégrer. L'objectif de cette thèse est d'améliorer la compréhension des marchés intégrés d'électricité et de leur comportement en fonction des caractéristiques et politiques de chaque pays. Un modèle de simulation est proposé pour étudier les conditions dans lesquelles l'intégration est désirable. Ce modèle est utilisé pour étudier trois cas d'interconnexion entre deux pays. Plusieurs politiques concernant l'expansion et l'opération de l'interconnexion, combinées avec différents mécanismes de rémunération de la capacité, sont évalués. Cette thèse est compose de trois articles. Le premier présente une description détaillée du modèle et une analyse du cas de la Colombie et de l'Equateur. Il montre que le couplage de marchés peut amener des bénéfices importants ; cependant, la différence de taille entre pays peut créer des soucis de dépendance aux importations pour le pays le plus petit. Le second papier compare le cas de la Colombie et l'Equateur avec le cas de la Grande Bretagne et de la France. Ces pays sont très différents en termes de ressources, taille des réservoirs d'accumulation pour l'hydro, complémentarité et croissance de la demande. Nos résultats montrent que la complémentarité joue un rôle essentiel dans l'obtention des bénéfices potentiels de l'intégration, alors qu'un taux élevé de croissance de la demande, ainsi qu'une grande capacité de stockage, mènent à des résultats contre-intuitifs, ce qui complique les décisions des régulateurs. Dans le troisième article, une extension du modèle présenté dans le premier article est utilisée pour analyser le cas de la Finlande et de la Russie. Différentes règles pour les échanges internationaux d'électricité sont considérées. Nos résultats indiquent qu'à un faible niveau d'interconnexion, la situation actuelle, où un marchand unique possède les droits de transmission et limite le flux pendant les heures de pointe, est bénéfique pour la Finlande. Cependant, en cas d'expansion de la capacité d'interconnexion, «market coupling» est préférable. préférable. Dans tous les cas, la Finlande a intérêt à garder une réserve stratégique, car même si cette politique entraine des coûts, elle lui permet de profiter des avantages de l'intégration tout en limitant ca dépendance envers les importations. En général, nous concluons que si les politiques adéquates sont implémentées, l'intégration des marchés électriques peut amener des bénéfices. Cependant, une grande capacité d'interconnexion n'est désirable que si les pays ont une complémentarité importante et il existe une confiance mutuelle. Les résultats des politiques qui cherchent à préserver la sécurité d'approvisionnement au niveau national peuvent être très contre-intuitifs, étant données les interactions entre les pays voisins et leurs effets sur les investissements en génération et en interconnexion. Il est donc très important pour les régulateurs de comprendre ces interactions et de coordonner décisions à fin de pouvoir profiter de l'interconnexion sans mettre en danger la sécurité d'approvisionnement. Mais il faut être conscients que même quand l'intégration amène de bénéfices pour la région, certains participants au marché sont perdants et pourraient essayer de bloquer le processus d'intégration.

Evolutionary Games in Networked Populations: Models and Experiments

Cooperation and coordination are desirable behaviors that are fundamental for the harmonious development of society. People need to rely on cooperation with other individuals in many aspects of everyday life, such as teamwork and economic exchange in anonymous markets. However, cooperation may easily fall prey to exploitation by selfish individuals who only care about short- term gain. For cooperation to evolve, specific conditions and mechanisms are required, such as kinship, direct and indirect reciprocity through repeated interactions, or external interventions such as punishment. In this dissertation we investigate the effect of the network structure of the population on the evolution of cooperation and coordination. We consider several kinds of static and dynamical network topologies, such as Baraba´si-Albert, social network models and spatial networks. We perform numerical simulations and laboratory experiments using the Prisoner's Dilemma and co- ordination games in order to contrast human behavior with theoretical results. We show by numerical simulations that even a moderate amount of random noise on the Baraba´si-Albert scale-free network links causes a significant loss of cooperation, to the point that cooperation almost vanishes altogether in the Prisoner's Dilemma when the noise rate is high enough. Moreover, when we consider fixed social-like networks we find that current models of social networks may allow cooperation to emerge and to be robust at least as much as in scale-free networks. In the framework of spatial networks, we investigate whether cooperation can evolve and be stable when agents move randomly or performing Le´vy flights in a continuous space. We also consider discrete space adopting purposeful mobility and binary birth-death process to dis- cover emergent cooperative patterns. The fundamental result is that cooperation may be enhanced when this migration is opportunistic or even when agents follow very simple heuristics. In the experimental laboratory, we investigate the issue of social coordination between indi- viduals located on networks of contacts. In contrast to simulations, we find that human players dynamics do not converge to the efficient outcome more often in a social-like network than in a random network. In another experiment, we study the behavior of people who play a pure co- ordination game in a spatial environment in which they can move around and when changing convention is costly. We find that each convention forms homogeneous clusters and is adopted by approximately half of the individuals. When we provide them with global information, i.e., the number of subjects currently adopting one of the conventions, global consensus is reached in most, but not all, cases. Our results allow us to extract the heuristics used by the participants and to build a numerical simulation model that agrees very well with the experiments. Our findings have important implications for policymakers intending to promote specific, desired behaviors in a mobile population. Furthermore, we carry out an experiment with human subjects playing the Prisoner's Dilemma game in a diluted grid where people are able to move around. In contrast to previous results on purposeful rewiring in relational networks, we find no noticeable effect of mobility in space on the level of cooperation. Clusters of cooperators form momentarily but in a few rounds they dissolve as cooperators at the boundaries stop tolerating being cheated upon. Our results highlight the difficulties that mobile agents have to establish a cooperative environment in a spatial setting without a device such as reputation or the possibility of retaliation. i.e. punishment. Finally, we test experimentally the evolution of cooperation in social networks taking into ac- count a setting where we allow people to make or break links at their will. In this work we give particular attention to whether information on an individual's actions is freely available to poten- tial partners or not. Studying the role of information is relevant as information on other people's actions is often not available for free: a recruiting firm may need to call a job candidate's refer- ences, a bank may need to find out about the credit history of a new client, etc. We find that people cooperate almost fully when information on their actions is freely available to their potential part- ners. Cooperation is less likely, however, if people have to pay about half of what they gain from cooperating with a cooperator. Cooperation declines even further if people have to pay a cost that is almost equivalent to the gain from cooperating with a cooperator. Thus, costly information on potential neighbors' actions can undermine the incentive to cooperate in dynamical networks.