In this paper we argue that a comparison of vowel systems of L1 and L2 should not be limited to measuring formants and vowel duration in speech production but should also include a contrastive... Show moreIn this paper we argue that a comparison of vowel systems of L1 and L2 should not be limited to measuring formants and vowel duration in speech production but should also include a contrastive study of the perceptual representations of the vowel systems entertained by native and non‐native users of the target language. An incorrect perceptual representation of the target sounds often lies at the heart of pronunciation difficulties of L2 speakers. To facilitate such perceptual research the present paper offers a universal vowel space in which 43 artificial sounds are sampled at perceptually equidistant steps along the dimensions of vowel height (7 steps), backness/lip rounding (9 steps). Duration can be added as an additional variable in as many steps as required by the researcher. The facility was provisionally tested in a study of the perceptual representation of the monophthongs of American English by American native listeners and by Persian learners of English. Several ways of analyzing the results of such a study are presented. The results show that native listeners distinguish tense and lax members of vowel pairs in English primarily by differences in vowel quality, while the Persian L2 listeners use vowel duration as the primary cue and largely ignore the quality cue. Show less