The purpose of this dissertation is to examine the perception of unstressed vowel reduction (UVR)--also known as vowel devoicing--in Central Mexican Spanish. UVR is a variable, gradient process in which vowels undergo a constellation of phonetic weakening processes including shortening, devoicing, and apparent deletion (Gordon 1998). While it is fairly common and has been well-studied in languages such as Japanese (Beckman and Shoji 1984) and Portuguese (Cunha 2015), its use is more limited in Spanish, and it is primarily associated with two regions: the highland plateau of Central Mexico and the Andean highlands. Although previous literature has examined the production of UVR in Spanish (Dabkowski 2018, Delforge 2008b) and the perception of UVR in other languages (Beckman and Shoji 1984, Meneses and Albano 2015), studies on the perception of UVR in Spanish are limited to Delforge's (2012) work on language attitudes in Cusco and a small-scale perception task in Perissinotto (1975). This leaves open multiple questions about how Spanish-speaking listeners perceive UVR, what factors influence their perception, and how UVR relates to issues of dialect perception and sociolinguistic awareness. This dissertation therefore seeks to provide an initial but wide-ranging view of the perception of UVR in Central Mexican Spanish by examining multiple aspects of listeners' perception. This was done by preparing a set of two perception experiments designed to test two overarching goals: first, how linguistic factors like phonetic variation, phonological context, and morphological context affect listeners' ability to perceive vowels; and second, what role UVR plays in listeners' dialect classification and language attitudes toward speakers. Additionally, questions of whether non-linguists notice UVR and whether listeners from different dialect areas differ in their perception were tested. The two perception experiments were administered online via Qualtrics, and a total of 84 participants completed either task, hearing a total of 1,558 stimuli and responding to a total of 8,648 question prompts. The results of these experiments contribute to our understanding of the perception of UVR in Spanish and cross-linguistically in several ways. Regarding linguistic factors, the different phonetic weakening processes of devoicing, shortening, and deletion were found to affect perception at different rates, supporting Dabkowski's (2018) claim that these processes are separate, providing insight into the dialectal distribution of these processes in Spanish, and demonstrating a need to consider these processes separately in future perceptual work. Low vowels and voiceless adjacent consonants were found to aid perception of weakened vowels, demonstrating an effect of phonological context on perception. And participants appeared to expect UVR in a plural -es ending, supporting Lipski's (1990) claim of a connection between morphology and UVR. Regarding sociolinguistic factors, listeners did use UVR in dialect identification, but they did so in unexpected ways, and listeners did not have strong social attitudes toward UVR, echoing similar results from production studies (Dabkowski 2018, Serrano 2006). Taken together, this dissertation offers an initial but thorough look at the perception of UVR in Spanish that complements previous production work in Spanish as well as previous perception work cross-linguistically. [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.]