Social applications on the Web have appeared as communication spaces for sharing knowledge and information. In particular, social applications can be considered valuable information sources because information in the applications is not only easily accessible but also revealing in that the information accrues via interactions between people. In this work, we address methods for finding relevant information in social media applications that use unique properties of these applications. In particular, we focus on three unique structures in social media: hierarchical structure, conversational structure, and social structure. Hierarchical structures are used to organize information according to certain rules. Conversational structures are formed by interactions within communities such as replies. Social structures represent social relationships among community members. These structures are designed to organize information and encourage people to participate in discussions in social applications. Accordingly, contexts extracted from these structures can be used to improve the effectiveness of search in social media relative to representations based solely on text content. To exploit these structures in retrieval frameworks, we need to address three challenges as follows. First, we should discover each structure because it is often obscure. Second, we need to extract relevant contexts from each structure because not all the contexts in a structure are relevant for retrieval. Last, we should represent each context or their combinations in a representation framework so that they can be encoded as retrieval components such as documents. In this work, we introduce an effective representation framework for multiple contexts. We then discuss how to discover or define each structure and how to extract relevant contexts from the structure. Using the representation framework, these relevant contexts are integrated into retrieval algorithms. To demonstrate that these structures can improve search in social media, the retrieval models and frameworks incorporating these structures are evaluated through experiments using data collections gathered from a variety of social media applications. In addition, we address two minor challenges related to social media search. First, it is not always easy to find relevant information from relevant objects if the objects are large. Accordingly, we address identification of relevant substructures in such objects. Second, text reuse structures are important since these structures have the potential to affect various retrieval tasks. In this thesis, we introduce text reuse structures and analyze text reuse patterns in real social applications.

The present research seeks to increase understanding of cognitive dissonance by exploring the various information sources that may influence the negative feelings that may arise during post-purchase evaluation. Specifically, the author focuses on the impact of consumer opinion seeking, traditional media search, internet search and social media search on cognitive dissonance by employing two studies. In Study 1, depth interviews are collected and analyzed in an effort to gain more insight into the search process and consumers perceptions of the helpfulness and credibility of different information sources. Categories of information sources, categories of which sources were deemed most helpful or credible, and categories of post-purchase evaluations as they relate to cognitive dissonance are drawn from the interviews. Conclusions are drawn from this analysis and a proposed model is provided informed by the emergent categories. The development of hypotheses is also discussed. Study 2 explores the impact of credibility of sources within social media on online furniture purchase decisions. A survey is developed to empirically examine the relationships represented in the model. A pretest is conducted with a sample of 207 respondents. The results of the pretest are used to make changes to the survey instrument for the main study. The main study is conducted using three samples of participants that gained information from one of three sources of information: 1) friends and family member, 2) retailer or 3) other individual (“others”) the participant does not know personally. The findings from the main study indicate that trustworthiness of the source positively impacts consumers’ perceptions of source credibility. Moreover, the results from each of the three samples also provide evidence that cognitive dissonance is less likely to occur when consumers have a positive attitude toward source of information. These findings are especially relevant for retailers as they should develop strategies to enhance trust among their customers in order to increase perceived credibility. In the same vein, retailers should focus on crafting approaches that foster favorable customer attitudes in order to reduce the occurrence of cognitive dissonance. Additional results of the main study are presented along with managerial implications and ideas for future research.