The present study examines whether listeners flexibly adapt to unfamiliar speech patterns such as those encountered in foreign-accented English vowels. In these cases, the relative informativity of acoustic dimensions (spectral quality vs. duration) can be changed such that the most informative dimension (spectral quality) is no longer informative, but the role of the secondary cue (duration) is enhanced. This study further tests whether listeners’ adaptive strategies are related to individual differences in utilizations of secondary cues (measured by phoneme categorization gradiency) and cognitive abilities. Native English listeners (N=36) listened to continuum of vowels /ɛ/ and /æ/ (as in head and had) varying spectral and duration values to complete a perceptual adaptation task, a visual analogue scaling (VAS) task, and were given cognitive ability tasks measuring inhibitory control, working memory, cognitive flexibility, and sustained attention. Our results showed that listeners mostly used spectral quality (primary cue) to signal vowel category at baseline. However, they rapidly adapted to unfamiliar speech by up-weighting reliance on duration (secondary cue) when spectral quality was no longer informative. The VAS task showed substantial individual differences in categorization gradiency with more gradient listeners using a secondary cue more, but categorization gradiency was not linked to degree of adaptation. Finally, results of cognitive ability tasks revealed that individual differences in inhibitory control, but not the other cognitive abilities, correlated with the amount of perceptual adaptation. Our presentation will discuss how these processing strategies are integrated to broaden our understanding of cognitive mechanisms in speech processing and language learning.