In public discourse around higher education, diversity based on socioeconomic status (SES) is often presented as an alternative to diversity based on race/ethnicity. In particular, the Supreme Court's 2023 ban on race-based affirmative action gave new energy to calls for SES-based diversity efforts. This dissertation seeks to uncover people's perceptions of SES diversity versus racial diversity and the downstream consequences of these perceptions. In the first chapter, I examine how people differentially apply moral and instrumental diversity rationales to the two diversity types. I find that among White (but not Black) Americans, SES diversity is moralized more than racial diversity. I then document a number of perceptions about the beneficiaries of either diversity type that underly this effect. In the second chapter, I show how moralization drives support for specific diversity efforts more so than instrumentalization, particularly for strong (vs. weak) diversity efforts. As such, given the differences in moralization, White Americans report greater support for strong SES-diversity policies than strong racial-diversity policies. In the last chapter, I investigate how people respond to institutional SES- and racial-diversity efforts. I find that White Americans exhibit more positive attitudes toward SES diversity and more negative attitudes toward racial diversity. Contrary to the hypotheses, Black Americans do not differentiate between the two diversity types. The current work contributes to the abundance of research on White Americans' cognitions about diversity, and speaks to the insights gained from studying diversity as a disaggregated construct. [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.]