  Acoustic context effects, where surrounding changes in pitch, rate or timbre
influence the perception of a sound, are well documented in speech perception,
but how they interact with language background remains unclear. Using a
reverse-correlation approach, we systematically varied the pitch and speech
rate in phrases around different pairs of vowels for second language (L2)
speakers of English (/i/-/I/) and French (/u/-/y/), thus reconstructing, in a
data-driven manner, the prosodic profiles that bias their perception. Testing
English and French speakers (n=25), we showed that vowel perception is in fact
influenced by conflicting effects from the surrounding pitch and speech rate: a
congruent proximal effect 0.2s pre-target and a distal contrastive effect up to
1s before; and found that L1 and L2 speakers exhibited strikingly similar
prosodic profiles in perception. We provide a novel method to investigate
acoustic context effects across stimuli, timescales, and acoustic domain.
