Social group disparities persist in who chooses to pursue Science, Technology, Engineering, and Mathematics (STEM) fields in higher education. Goal congruity theory has highlighted how perceptions of other-oriented opportunities in STEM can spur interest among underrepresented students. The present work extends this framework by considering how perceptions of social identity development opportunities might also promote belonging and drive interest in STEM. Three studies test this prediction with a particular emphasis on LGBTQ students in STEM. Study 1 explores how perceived identity development opportunities within a students' academic major relate to their felt belonging. Study 2 shifts to perceptions of other academic majors and examines three possible cues to identity development opportunities that are hypothesized to vary across STEM and social sciences and humanities majors. Finally, Study 3 experimentally manipulates the presence of critically reflective and reflexive activities within introductory STEM courses. The value of considering social identity development affordances and motives in extending both goal congruity and identity development perspectives is discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]