abstract: A pressing question in public policymaking is how best to allocate decision-making authority and to facilitate opportunities for input. When it comes to science, technology, and environmental (STE) policy decisions, persons impacted by those decisions often have relevant information and perspectives to contribute yet lack either the specialized, technical knowledge or the means by which to effectively communicate that knowledge. Consequently, due to a variety of factors, they are frequently denied meaningful involvement in making them. In an effort to better understand why this is so, and how this might change, this dissertation uses an activity systems framework to examine how three factors mediate the circulation of information in STE public engagement mechanisms. In this project, I examine the transcripts of a 2015 administrative hearing and community meeting about the Santa Susana Field Lab—a former nuclear- and rocket engine-testing facility 30 miles from Los Angeles, where an experimental nuclear reactor suffered a partial meltdown in 1959. Specifically, I identify (1) who was designated as an "expert" versus a member of "the public," (2) the structural features, and (3) the stylistic features of participants' remarks at these events; and I study how these factors mediated the flow of information at each. To do so, I view "expert" and "public" as what Michael McGee has termed ideographs, and consider the structural and stylistic features that prior scholarship has identified to impact information flow. Based on my analysis, I theorize that role designations, structural features, and stylistic features work together to mediate whose, what, and how information flows in public engagement mechanisms. Based on my findings, I also suggest that this mediation impacts policy outcomes. As such, I contend that better understanding the relationships among these mediational means, information flow, and policy outcomes is an important step towards developing public engagement mechanisms that most effectively use the relevant knowledge and other insights of all who have a stake in policy decisions. / Dissertation/Thesis / Doctoral Dissertation English 2016