German has a set of high front rounded vowels, /yː, ʏ/, that are difficult for second language (L2) learners to acquire. They are often misperceived by L2 learners as back vowels. Many models explain the initial perceptual assimilation of L2 segments into first language (L1) segments, but it is unclear how acquisition occurs in the articulatory domain. This study investigates the acoustic-articulatory acquisition of high vowels in German by L1 speakers of Polish. We collected acoustic and ultrasound data for learners at the A-level (beginner), B-level (intermediate), and C-level (advanced) to examine how articulatory acquisition progresses. The findings indicated assimilation of German /yː, ʏ, ʊ/ to Polish /u/ for A-level learners. Differences emerge at the B-level, and at the C-level we observed robust contrasts. The data indicates that L2 segmental acquisition is a long process and that, for perceptually similar segments, L2 learners appear to harvest their L1 articulations and modify them until the contrast is acquired.
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