For decades, programs targeting the recruitment and retention of underrepresented minorities (URM) have had local success in broadening participation in the geosciences. Meanwhile, national graduation rates of URM geoscience majors fall below the national graduation rates of URM STEM majors, generally. In this literature review, we summarize methods used to investigate the efficacy of geoscience recruitment and retention programs, and we propose avenues of future investigation into why programs are successful. First, we categorize a decade of recent publications in the "Journal of Geoscience Education" (JGE) according to Astin's Input-Environment-Output (IEO) model. This model offers a classification scheme to evaluate how inputs (e.g., student characteristics) and environment (e.g., program attributes) may influence desired outputs (e.g., results of programs). Next, we discuss a set of social, cognitive, and psychological theories that support deeper investigation into the reasons why recruitment and retention programs are successful with particular groups. There is an observable trend in the geoscience literature after 2009 toward interventions that include all components of the IEO model and random assignment (i.e., "natural experiments"). We argue that self-efficacy, identity, microaggressions, stereotype threat, and social cognitive career theory offer perspectives that can guide future programmatic interventions and support the geoscience community in broadening participation in the geosciences.