It is insufficiently realized in the teaching of the phonetics of foreign languages that studying the acoustics of the vowel systems per se, as was done in section 2, does not reveal the full organization of a vowel system, and – more importantly – does not reveal the (often incorrect) perceptual representation of the vowel system of the target language. What is needed to appreciate the representation of the vowel system in the mind of the learner (and of the native speaker) is a perceptual mapping. Using perceptual techniques allows the researcher to establish so‐called trading relationships between the parameters that define the individual listener’s vowel space.