Coda /s/ weakening is among the most studied phonological phenomena in Spanish, and variationists have shown that /s/ weakening and complete deletion are conditioned by many factors. Though complete deletion of a plural /s/ may occasion homophony with singular items in Spanish, few studies have examined the acoustic and prosodic cues that speakers may use to signal plurality when a final /s/ is deleted. In this dissertation, I explore cues used by speakers and listeners of Chilean Spanish, an /s/ weakening variety, to distinguish plural from singular Noun Phrase (NP) constituents in both speech production and perception. I analyze acoustic cues of duration, vowel quality, and breathiness from the sociolinguistic interviews of 60 Santiago residents grouped by age and gender, comparing singular word-final vowels to plural word-final vowels with the final /s/ completely deleted. These 60 participants also took part in a two-alternative forced-choice perception task, asked to identify plurality on isolated natural stimuli extracted from sociolinguistic interviews. I determined that utterance-medial vowel shortening is a cue for plurality, produced and perceived by only members of the middle age groups across genders and SES groups demonstrating age grading and overall community stability. Additionally, breathiness is a prestigious cue for plurality produced and perceived reliably by high SES speaker-listeners, and produced by younger members of the lower SES as well, though these low SES speakers do not perceive breathier vowels as plural. I posit that these younger speakers are adopting the use of breathy plural vowels in a change from above, and that the mismatch between production and perception signals the instability of the nascent change. Utterance-final lengthening is produced but not perceived by young females in the low SES, while middle- and older age group females in this neighborhood perceive breathier vowels as plural but do not produce them as such. Again, I posit that this mismatch signals instability of this cue as it is begun as a change from below by these low SES female speakers. Finally, plural vowel lowering is produced only by young males in the high SES group, but is perceived by all males and young females in both SES groups. It is therefore a perceptually robust but seemingly unreliable cue, signaling some type of instability. Plural vowel raising, on the other hand, is produced by middle- and older age group speakers in the lower SES, but not perceived by any groups. I therefore posit that plural raising is moving toward loss, as younger speakers in the low SES do not produce their singular and plural vowels with any F1 differences.
In sum, this dissertation contributes findings from both production and perception, offering the first acoustic evidence for shifts in multiple directions of the several cues that mark the singular~plural distinction in this /s/ weakening dialect of Spanish.