Date of Award:

8-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Computer Science

Committee Chair(s)

Vicki H. Allan

Committee

Vicki H. Allan

Committee

Scott Cannon

Committee

Xiaojun Qi

Committee

David E. Brown

Committee

Curtis Dyreson

Abstract

This dissertation investigates weighted voting games and three methods of manipulating those games, called splitting, merging, and annexation. The manipulations involve an agent or some agents misrepresenting their identities in anticipation of gaining more power over the outcomes of games. Indeed, in open anonymous environments, manipulation can be easy and cheap to achieve. We provide clear and sufficient discussion on related work and backgrounds to motivate this research topic, which certainly deserves attention. Weighted voting games are among key cooperative games, and the manipulations considered in this dissertation are natural, and have practical applications, that are likely to raise interests in the game theory and artificial intelligence communities.

We provide interesting theoretical and simulation results for the two broad classes of weighted voting games - unanimity and non-unanimity weighted voting games. In the anaylses and experiments, the following prominent power indices are considered to measure the influence of players: Shapley-Shubik, Banzhaf, and Deegan-Packel. The results we propose in this work fit under the models of deception and fraud, as well as models and mechanisms for establishing identities. If an agent can increase its power, as evidenced by a power index, it is more likely to employ any of these forms of manipulation, and it becomes difficult to maintain trust. Thus, awareness of various levels of power indices susceptibility to manipulation allows users to informatively select a power index. This provides some assurance of identity, which is crucial for establishing and maintaining trustworthy interactions. This study also increases our indepth understanding of these manipulations in weighted voting games and their effects, which may provide insights that are needed in the development of methods to reduce the effects of the menace in the future.

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