Thesis (Ph.D.) - Indiana University, Department of Speech, Language, and Hearing Sciences, 2022A central issue in the study of speech perception is how listeners resolve the vast amount of variability present in speech signals. Gender diversity presents an opportunity to examine how listeners learn and represent one dimension of sociophonetic variability arising from an evolving social category, speaker gender. In this dissertation, a speech corpus of scripted and unscripted utterances was created inclusive of speakers with varying gender identities (e.g., non-binary, transgender men, and transgender women). Read utterances from the corpus were used in an auditory free classification paradigm, in which listeners categorized the speakers on perceived general similarity and gender identity. Cluster and multidimensional scaling analyses were used to ascertain listeners’ perceptual organization of speakers. Cluster solutions for listeners’ categorizations of general similarity revealed a complex hierarchical structure in which speakers were broadly differentiated based on gender prototypicality, and more finely differentiated by masculinity/femininity, age, dialect, vocal quality, and suprasegmental features. Further, listeners used different organizing factors depending on perception of speaker gender. In contrast, cluster solutions for categorizations of gender identity were simplified and demonstrated listeners’ attention to gender prototypicality and masculinity/femininity. Multidimensional scaling analyses revealed two-dimensional solutions, in which listeners demonstrated gradient organization of speakers for each dimension, as the best fit for all free classifications. The first dimension was interpreted as masculinity/femininity, where listeners organized speakers from high to low fundamental frequency and first formant frequency. The second was interpreted as gender prototypicality, where listeners separated speakers with fundamental frequency and first formant frequency at upper and lower extreme values (prototypical) from more intermediate values (non-prototypical). Results suggest that listeners engage in fine-grained analysis of speaker gender that cannot be adequately captured by a “male” versus “female” dichotomy. Assumptions of a gender binary in the study of speech communication may require a critical re-examination to accommodate multidimensional and gradient representation of speaker gender.