Multimedia Social Networks: Game Theoretic Modeling and Equilibrium Analysis

Multimedia content sharing and distribution over multimedia social networks is more popular now than ever before: we download music from Napster, share our images on Flickr, view user-created video on YouTube, and watch peer-to-peer television using Coolstreaming, PPLive and PPStream. Within these multimedia social networks, users share, exchange, and compete for scarce resources such as multimedia data and bandwidth, and thus influence each other's decision and performance. Therefore, to provide fundamental guidelines for the better system design, it is important to analyze the users' behaviors and interactions in a multimedia social network, i.e., how users interact with and respond to each other. Game theory is a mathematical tool that analyzes the strategic interactions among multiple decision makers. It is ideal and essential for studying, analyzing, and modeling the users' behaviors and interactions in social networking. In this thesis, game theory will be used to model users' behaviors in social networks and analyze the corresponding equilibria. Specifically, in this thesis, we first illustrate how to use game theory to analyze and model users' behaviors in multimedia social networks by discussing the following three different scenarios. In the first scenario, we consider a non-cooperative multimedia social network where users in the social network compete for the same resource. We use multiuser rate allocation social network as an example for this scenario. In the second scenario, we consider a cooperative multimedia social network where users in the social network cooperate with each other to obtain the content. We use cooperative peer-to-peer streaming social network as an example for this scenario. In the third scenario, we consider how to use the indirect reciprocity game to stimulate cooperation among users. We use the packet forwarding social network as an example. Moreover, the concept of ``multimedia social networks" can be applied into the field of signal and image processing. If each pixel/sample is treated as a user, then the whole image/signal can be regarded as a multimedia social network. From such a perspective, we introduce a new paradigm for signal and image processing, and develop generalized and unified frameworks for classical signal and image problems. In this thesis, we use image denoising and image interpolation as examples to illustrate how to use game theory to re-formulate the classical signal and image processing problems

Device-to-device communications: a performance analysis in the context of social comparison-based relaying

Device-to-device (D2D) communications are recognized as a key enabler of future cellular networks which will help to drive improvements in spectral efficiency and assist with the offload of network traffic. Among the transmission modes of D2D communications are single-hop and relay assisted multi-hop transmission. Relay-assisted D2D communications will be essential when there is an extended distance between the source and destination or when the transmit power of D2D user equipments (UEs) is constrained below a certain level. Although a number of works on relay-assisted D2D communications have been presented in the literature, most of those assume that relay nodes cooperate unequivocally. In reality, this cannot be assumed since there is little incentive to cooperate without a guarantee of future reciprocal behavior. Cooperation is a social behavior that depends on various factors, such as peer comparison, incentives, the cost to the donor and the benefit to the recipient. To incorporate the social behavior of D2D relay nodes, we consider the decision to relay using the donation game based on social comparison and characterize the probability of cooperation in an evolutionary context. We then apply this within a stochastic geometric framework to evaluate the outage probability and transmission capacity of relay assisted D2D communications. Through numerical evaluations, we investigate the performance gap between the ideal case of 100% cooperation and practical scenarios with a lower cooperation probability. It shows that practical scenarios achieve lower transmission capacity and higher outage probability than idealistic network views which assume full cooperation. After a sufficient number of generations, however, the cooperation probability follows the natural rules of evolution and the transmission performance of practical scenarios approach that of the full cooperation case, indicating that all D2D relay nodes adopt the same dominant cooperative strategy based on social comparison, without the need for enforcement by an external authority

Cooperation in a dynamic social environment

Cooperative behaviour among unrelated individuals is an evolutionary paradox. Research suggests that an individual’s propensity to cooperate and its response to experiencing cooperation or defection from its social environment consistently varies among individuals and as a function of external factors. The biological and psychological underpinnings of such behavioural variation remain unknown; they can, however, provide more insight into the evolution and maintenance of cooperation among non-kin. This thesis explores the proximate effects of experiences of cooperation or defection from the social environment, as well as possible proximate drivers of cooperative behaviour, using the Trinidadian guppy (Poecilia reticulata) as a study system. Firstly, the behavioural rules underpinning an individual’s decision to cooperate or not with unfamiliar individuals in the presence of specific or non-specific information were explored. When fish had information about their social partner’s cooperativeness, they behaved in a manner consistent with direct reciprocity, copying their partner’s last move. When paired with an ostensibly novel partner, a different, or at least additional, behavioural rule seemed to be employed. In order to help understand the drivers of individual variation in cooperative behaviour, phenotypic selection on cooperativeness was carried out over three filial generations, resulting in fish of high cooperativeness (HC) and low cooperativeness (LC). The divergence of individual cooperativeness observed between the two phenotypic selection lines suggests that cooperative behaviour in the context of predator inspection is at least in part heritable. Cooperative behaviour of F3 fish was found not to correlate with boldness or exploratory behaviour; HC and LC fish did, however, differ in some aspects of sociability and agonistic behaviour. Possible proximate neuromodulatory mechanisms underlying these differences in cooperativeness were also explored, focusing on brain expression patterns for the isotocin receptor (itr) gene in F3 females. HC females were found to have higher mid-section itr expression levels than LC females. Finally, I explored the effects of experiencing cooperation or defection on monoaminergic neurotransmission, which is thought to instantiate the effects of such experiences on the individual’s internal state. My findings suggest that experiencing cooperation or defection from the social environment affects internal state; this phenomenon may be crucial for the appropriate adjustment of the behavioural response to such experiences, and for the emergence of behavioural rules such as generalised reciprocity. Taken together these results suggest that neuromodulatory mechanisms are pivotal for the perception of stimuli from the social environment in the tested cooperative context and that variation in cooperative behaviour may be underpinned by individual differences in the structural properties of such systems. They also provide insight into how behavioural input may affect the behavioural response to such experiences, and ultimately how such mechanisms may lead to the evolution and maintenance of cooperation.Danish Council for Independent Researc

On the Nature, Modeling, and Neural Bases of Social Ties

This paper addresses the nature, formalization, and neural bases of (affective) social ties and discusses the relevance of ties for health economics. A social tie is defined as an affective weight attached by an individual to the well-being of another individual (‘utility interdependence’). Ties can be positive or negative, and symmetric or asymmetric between individuals. Characteristic of a social tie, as conceived of here, is that it develops over time under the influence of interaction, in contrast with a trait like altruism. Moreover, a tie is not related to strategic behavior such as reputation formation but seen as generated by affective responses. A formalization is presented together with some supportive evidence from behavioral experiments. This is followed by a discussion of related psychological constructs and the presentation of suggestive neural findings, based on the existing literature. We conclude with some suggestions for future research. Publication forthcoming in 'On the Nature, Modeling and Neural Bases of Social Ties', Daniel E. Houser and Kevin A. McCabe (eds), Neuroeconomics, Advances in Health Economics and Health Services Research, Emerald Insight Publishing

Neural mechanisms underlying interindividual differences in intergenerational sustainable behavior.

Intergenerational sustainability is a pressing challenge, which is exacerbated by the fact that the current generation must make sacrifices today to ensure the well-being of future generations. There are large interindividual differences in intergenerational sustainable behavior. However, the neural mechanisms underlying these interindividual differences have remained unexplored. Here, we combined fMRI with a consequential intergenerational sustainability paradigm in a sample of 72 healthy students. Specifically, we analyzed task-dependent functional activity and connectivity during intergenerational sustainable decision-making, focusing on the state-like neurophysiological processes giving rise to behavioral heterogeneity in sustainability. We found that differences in neural communication within and between the mentalizing (TPJ/DMPFC) and cognitive control (ACC/DLPFC) network are related to interindividual differences in intergenerational sustainable behavior. Specifically, the stronger the functional connectivity within and between these networks during decision-making, the more individuals behaved intergenerationally sustainably. Corroborated by mediation analyses, these findings suggest that differences in the engagement of perspective-taking and self-control processes underly interindividual differences in intergenerational sustainable behavior. By answering recent calls for leveraging behavioral and neuroscience for sustainability research, we hope to contribute to interdisciplinary efforts to advance the understanding of interindividual differences in intergenerational sustainability

Neural and Cognitive Basis of Third-Party Altruistic Decision-Making and Its Modulators

Human beings live in a world full of social connections. Favoring by the evolution, humans could survive the challenges of nature by not only maximizing their own interests (i.e., selfish motives) but also by considering the well fare of others even at a cost to their own resources (i.e., altruistic motives). Beyond the kindness between relatives and direct reciprocity between friends, humans, as third-party bystanders, will sometimes engage in a costly situation where social norms are vio-lated, to achieve justice via either punishing the unknown offender or compensating the anony-mous victim, even when such a violation does not directly affect their own interests and the costs incurred by them will not be paid back. Why do unaffected third parties intervene at a personal cost and what might be the underlying neural as well as cognitive mechanism? What factors might influence their decisions in such situations? To address these questions, the present dissertation used four studies by adopting a modified third-party economic paradigm to capture the third-party altruistic behaviors (i.e., third-party help and punishment) in response to an unfair situation, with the help of the technique of functional magnetic resonance imaging (fMRI; Studies 1-3) and eye-tracking (Study 4). By mainly investigating neural correlates during altruistic decision-making of third parties, Study 1 showed that signals in the bilateral striatum (esp. the ventral part) were stronger when third-party deciders chose to either help the victim or punish the selfish offender. Further analyses revealed an association between either choice of altruistic behavior, or its neural activation, and the empathic concern level, a personality trait closely related with altruism (esp. helping behavior). Studies 2-4 further tested whether, and how, other factors modulate third-party decision-making and the underlying neural or cognitive processes. In particular, Studies 2A and 2B focused on oxytocin, a so-called ―pro-social‖ hormone, and tested whether its effect on other altru-istic behaviors extended to the third-party context. As revealed by Study 2A, and replicated by Study 2B, we observed that intranasal oxytocin affects neither type of third-party altruistic deci-sions; rather, it modulated neural processing, especially via enhancing activity in the temporo-parietal junction (TPJ), a region shown to support mentalizing ability, during the perception of helping decision made by a computer (Study 2A). Study 3 manipulated the attention focus on different aspects of the norm violation (i.e., asking participants to consider either the unfairness of the offender or the feelings of the victim), and showed not only an effect on third-party altruistic choice behavior, but also confirmed the role of TPJ and control-related regions in such modula-tion. Replicating the effects of empathic concern (Study 1) and attention focus on choice behavior (Study 3), Study 4 provided the first empirical evidence that eye-movement pattern during third-party altruistic decision-making could also be biased by both factors and their interaction, shed-ding light on the cognitive mechanism underlying attention and information searching. Limitations of the studies and future research directions were also discussed

Social neuroscience in psychiatry: unravelling the neural mechanisms of social dysfunction

Social neuroscience is a flourishing, interdisciplinary field that investigates the underlying biological processes of social cognition and behaviour. The recent application of social neuroscience to psychiatric research advances our understanding of various psychiatric illnesses that are characterized by impairments in social cognition and social functioning. In addition, the upcoming line of social neuroscience research provides new techniques to design and evaluate treatment interventions that are aimed at improving patients’ social lives. This review provides a contemporary overview of social neuroscience in psychiatry. We draw together the major findings about the neural mechanisms of social cognitive processes directed at understanding others and social interactions in psychiatric illnesses and discuss their implications for future research and clinical practice