Despite the demand for a diverse STEM-educated population and workforce, college students have consistently turned away from these disciplines in large numbers, creating a persistent problem that many are trying to address. The aim of the National Science Foundation's Research Experiences for Undergraduates (REU) program is to inspire, attract, and retain STEM majors. Funding supports undergraduate STEM students' engagement in real-world research alongside STEM mentors. As colleges and universities compete for funding for REUs, it is important to understand the mechanisms within summer research programs that resonate most deeply with undergraduate STEM researchers. While many studies reveal strong correlations between research experiences and STEM aspirations, less is known about the mechanisms within REU programs that support these gains. My research used quantitative and qualitative self-reported data from 20 REU students, 18 of whom were underrepresented minorities in STEM. Over two summers, these students, in cohorts of ten, came to the University of Vermont to participate in a team-oriented, 10-week REU: Interdisciplinary Research on Human Impacts in the Lake Champlain Ecosystem. Two mixed-methods studies, guided by the frameworks of the theory of possible selves, theory of self-efficacy for research, and social cognitive career theory, revealed four important program mechanisms that gave rise to gains in research skills, confidence and self-efficacy for research, and STEM career aspirations, particularly for individuals from underrepresented minority groups in STEM. Findings suggest that the program fostered student capacity building within a safe, inclusive, and positive setting where students experienced what it feels like to be an active participant in the world of research. Within this context, critical mechanisms that gave rise to gains in research skills, confidence and self-efficacy for research, and STEM career aspirations included: (1) experiential education through interdisciplinary research experiences, (2) student independence and ownership balanced with expert researcher guidance and support, (3) formal and informal mentoring networks where students were mentored and where they mentored others, and (4) the establishment of an intentional learning community that advanced leadership, research skill building, perseverance, and reflection. Results from this research cannot be generalized beyond the context of the Lake Champlain REU, however, findings are in alignment with the body of literature that highlights the positive effects of REUs on STEM majors' research skills, confidence and self-efficacy for research, and STEM career aspirations. Using mixed methods to identify and understand the within-program mechanisms that support student gains is a valuable new research approach for this field. Recognizing programmatic mechanisms across REU programs can lead to expansion, replication, and application of these models beyond one institution, resulting in more positive gains for more undergraduate STEM researchers.

With increasing numbers of first-generation college students enrolling in colleges and universities across the US, so too is the need to begin preparing such underrepresented students for graduate school and a career in academia. As a phenomenological case study of student transformation, this dissertation examines the experience of nine first-generation college students in the summer research portion of the Ronald E. McNair Achievement Program (McNair) at University of Arizona. The qualitative data collected includes in-depth interviewing, observing the students' in-class presentations on the progress of their summer research, and reviewing the students' written work. Drawing on Adult Transformational Learning Theory (Mezirow, 1991) and Gee's writings on student identity (2000) and Discourse (2005), this study primarily addresses the following questions: 1) How do UA McNair students take on and use the Discourse of research during the 10 week summer program? And 2) as they engage in the Discourse of research (in classes, with mentors, with peers, in written work), what academic identity transformations are observed (in the classroom, in interviews, and in written work)? Narrative inquiry (Clandinin & Connelly, 2000) was utilized to organize and examine the data, and research texts consist of academic biographies written for each student. Findings reveal that student transformation is the noticeable difference in the students' utilization and integration of a language system used to describe their summer research and to define their research interests. Defined as the Discourse of research, this becomes the basis for students enacting the identity of undergraduate researcher. As a cohort of nine McNair Scholars, students share the experience of undergraduate research and engage in conversations which address the insecurities they have as first-generation college students. Through this formation of an affinity group (Gee, 2005) and their utilization of the Discourse of research, students engage in critical reflection, reevaluate their academic identities, and begin preparing themselves for their transition from undergraduate students to first-year doctoral students.