This dissertation investigates whether people possess knowledge of fine-grained distinctions among the sonority levels that are unattested in their language. Specifically, I investigate the whether people encode the putatively universal distinction between the sonority levels of fricatives and stops. Across languages, fricatives and stops differ in their sonority levels. Productive phonological alternations in English, however, do not make this distinction. The present research examines whether English speakers nonetheless consider fricatives more sonorous than stops. The following research infers the sonority levels of fricatives and stops from their sonority distance. To gauge English speakers' knowledge of the sonority levels of fricatives and stops, onsets with rising sonority (e.g., "fn, pn") were thus compared to matched onsets with level sonority (e.g., "fs" or "pt"). Given that English speakers misidentify ill-formed monosyllables with small sonority distances as disyllabic (Berent et al., 2007), and that the rise in fricative-nasal onsets is smaller than the rise in stop-nasals ones, one would expect the rate of misidentification for rises and plateaus to be more similar for fricative-initial monosyllables compared to stop-initial ones. Therefore, when compared to matched sonority plateaus, stop-nasal monosyllables should be identified more accurately than fricative-nasal ones: people should identify them more readily as monosyllables, and more accurately distinguish them from disyllabic counterparts. Four experiments compared English speakers' perception of sonority distance in onsets composed of either stops or fricatives. In Experiments 1-2, participants determined if an auditory non-word (e.g., "fnik; fenik") had one syllable or two. Monosyllables with a stop-initial onset of rising sonority (e.g., "pnik") yielded more accurate responses than stop-initial monosyllables with a sonority plateau (e.g., "ptik"). In contrast, responses to fricative-initial monosyllables with rising (e.g., "fnik") and level (e.g., "fsik") sonority did not differ. In Experiment 3, participants determined if a pair of auditory stimuli (e.g., "pnik-penik; fnik-fenik") was identical. Non-identical trials with sonority rises elicited faster responses than plateaus given items comprising stop-initial, but not with fricative-initial onsets. These results are consistent with the prediction that the sonority distance between fricative-initial onsets is attenuated relative to stop-initial ones, and consequently, English speakers consider fricatives more sonorous than stops. It is possible, however, that such misidentifications reflect an inability to perceive the phonetic properties of stop-onsets relative to fricative-ones. But, the results from Experiment 4 with printed materials countered this interpretation. In this experiment, people remained sensitive to the sonority level of the onset--a stop or a fricative--even when presented with printed monosyllables, inputs that carry no phonetic information. In particular, the identification of printed stop-initial items was modulated by sonority distance, whereas no such effect was observed for fricative-initial ones. Overall, the results are consistent with the prediction that English speakers consider fricatives more sonorous than stops. If the ranking of the sonority levels of fricatives and stops cannot be learned from experience in English, then the English findings would suggest that speakers universally represent fricatives as more sonorous than stops. To gauge universality, additional analyses examined evidence for the distinction between fricatives and stops in the English lexicon. The results showed that the sonority distinction between fricatives and stops cannot be captured by the co-occurrence of features in English, as performance was selectively modulated by sonority-relevant distinctions. Specifically, people were indifferent to the co-occurrence of features irrelevant to sonority (e.g., place), but sensitive to the co-occurrence of features relevant to sonority (e.g., manner). Nonetheless, the English results do not necessarily require that the ranking of the sonority levels of fricatives and stops be universally specified. Additional analyses showed that, if the grammar was equipped with substantive knowledge related to sonority (including knowledge that sonorants are "more" sonorous than obstruents, knowledge that obstruents comprise both fricatives and stops, and a preference for onsets with large sonority distances), then English speakers could potentially use their lexical experience to infer that fricatives are more sonorous than stops. 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