Date of Award

Spring 2021

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Dovidio, John


Given the increasing prevalence of social media in people’s social lives, understanding the dynamics of interpersonal interaction online is timely and important, both theoretically and practically. One key element in these dynamics is the way people identify themselves online. Identity can influence how people see themselves and others, as well as how people treat others. One way through which people create or claim an identity online is through the use of a pseudonym: a self-designed identifier that is used in place of one’s actual name. My dissertation investigates how Internet users come to value persistent online identifications, such as pseudonyms, as extensions of self and how this process shapes online behavior. The specific goals of this dissertation are to investigate how (a) pseudonymous settings online influence prosociality relative to anonymous settings, and (b) different features of pseudonyms, such as their persistence and level of expressiveness, can change people’s expectations for their own and others’ identifiability and thereby influence behavior and attitudes. This dissertation also studies how personality factors, social context, and group identity can serve to moderate the effects of pseudonymity on behavior and attitudes. The dissertation pursues these goals across six chapters. Chapter 1 introduces the key concepts and objectives in the dissertation. Chapter 2, which contrasts pseudonymity and anonymity, reviews the existing literature and outlines theoretical considerations that inform subsequent study designs. Chapter 2 explains how pseudonymity may make personal and group identities salient, and how personal and situational factors may interact with pseudonymity to influence behavior. Chapter 3 investigates in two studies how prosocial behavior online may be influenced through the use of personal identifiers. These two studies distinguish the effects of anonymity from pseudonymity (Study 1) between temporary and persistent pseudonymity (Studies 1 and 2) in online behavior. The results of Study 1 and Study 2 suggest that the effects of having a pseudonym, compared to being anonymous, or having a persistent versus temporary pseudonym, influence prosocial behavior primarily by affecting perceptions of recognizability. Chapter 4 presents an experiment (Study 3) that investigated how qualities of persistent pseudonyms can affect users’ psychological states and ultimately their online social behavior. It explored the effect of a pseudonym that contained “unique” personally-relevant information or one that was personally relevant but also is designed to be expressive of oneself, compared to a control condition in which participants had a persistent pseudonym that was designed to individuate them (a pseudonym that distorts personal information in an unrecognizable fashion), on online social experiences and behavior. Although, as expected, participants valued unique and expressive pseudonyms more than information pseudonyms and found expressive pseudonyms as being more personally reflective, inconsistent with expectations, unique and expressive pseudonyms did not make participants feel more recognizable to others than did information pseudonyms. Chapter 4 describes Studies 4 and 5 that further considered prosociality and group dynamics. Study 4 included an additional manipulation of others’ recognizability and a measure of participants’ concerns about leaving a good impression on others, and it also investigated participants’ everyday sadism as a moderator of prosociality. Guided by findings from Study 4, Study 5 manipulated the perceived group membership of participants and included other aspects of altruistic punishment (Fehr & Gächter, 2002) as behavioral measures. These two studies indicated that there may be an optimal amount of personal information to receive about another person online—particularly when one does not feel a strong sense of ingroup cohesion with this other person. When individual identities were emphasized, individuating information about others online appeared to be “too much information,” which discouraged prosocial feelings. By contrast, when group identity was salient, receiving personal information about others did not reduce prosociality relative to not receiving such information. Chapter 6 discusses implications, limitations, and future directions of my research. In particular, Chapter 6 compares the results of the studies to existing literature and explains the studies’ novel contributions, while also acknowledging their shortcomings. Chapter 6 then proposes future studies for testing wider implications of the dissertation research. Ultimately, I expect that my work will contribute to the psychological understanding of online social interaction, particularly in the context of identity, and that its implementation will help both website administrators and users to create social spaces that are safer, more collaborative, and more enjoyable to use.