Motivated by the underrepresentation of women in math-related majors and occupations, the present dissertation explored the possibility that disparities in frequency of classroom participation--a measure of engagement prone to gender differences--could be partially responsible for gender differences in belonging and identity in math contexts. Via the introduction of a novel psychological construct, "class participation confidence threshold," and the adoption of a Regulatory Focus Theory framework, the present work aimed to investigate mechanisms underlying gender differences in math classroom participation, as well as how these disparities might contribute to more distal outcomes. The dissertation consisted of two studies conducted with undergraduate students. Both studies tested a theoretical model that posited potential predictors and outcomes of gender differences in classroom participation. Study 1 (N = 161) was a cross-sectional investigation of students' participation frequency, reported based on their general experience in current math and social science classes. Study 2 (N = 269) investigated the same associations using a daily diary methodology, including pre- and post-measures of relevant constructs. Results indicated that, when considering opportunities for participation, women participated less than men--both in math and the comparison domain of social science. In addition to less frequent participation, women generally displayed higher stereotype threat susceptibility and confidence thresholds in both domains. Women also demonstrated higher levels of a prevention focus in math compared to social science, while men's regulatory orientation was similar across domains. With respect to the proposed outcomes of participation (i.e., belonging, identity, and career interest), women exhibited lower levels than men in math and equal or higher levels in social science. Path analyses revealed that students' regulatory focus predicted their classroom participation and that this relation was mediated by their confidence threshold. Importantly, these results persisted even when controlling for motivational variables traditionally regarded as predictors of classroom participation according to Expectancy-Value Theory. The results suggest that an increased prevention focus in the math domain may lead women to set higher confidence thresholds and participate less frequently. [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.]