I’ve heard that one before: Phonetic reduction in speech production as a possible contributing factor in perceptual illusory vowel effects

Abstract This study probed the relationship between productive phonotactic repair and speech production, by asking whether the natural variability found in speech, through phonetic reduction, may include apparent illicit sequences requiring repair, even though the target words are licit. Spanish productively repairs word-initial /s/-consonant clusters (#sC) with a prothetic [e] in both production and perception. We asked whether the initial vowel in Spanish #VsC words like espalda ‘back’ is prone to reduction, and whether or not /e/, which matches the default repair vowel, is more susceptible to reduction than other vowels (e.g. in aspirina ‘aspirin’) due to its predictability. We explore these hypotheses in the speech of 11 speakers of Andalusian Spanish who produced #VsC words in isolation. Initial vowels showed lower intensity, greater devoicing, and less modal voicing compared to control #pVs-initial words, and initial /e, i, o/ were occasionally deleted, leading to the occurrence of apparently illicit sequences in actual speech, e.g. espalda produced as [spalda]. However, evidence that the default vowel, [e], was reduced more than other vowels was weak. These results suggest that variation in speech may contribute to the well-known illusory vowel effects, where listeners perceive illicit sequences as though the repair vowel had been present.