Perception of natural productions of two German vowels contrasts, /y/ vs /u/ and /Y/
vs /U/, was examined in monolingual English-speaking adults. Subjects were tested
on multiple exemplars of the contrasting vowels produced in a dVt syllable by a native
German speaker. Discrimination accuracy in an AXB discrimination task was well above
chance for both contrasts. Most of the English adults failed to attain "nativelike"
discrimination accuracy for the lax vowel pair /U/ vs /Y/, whereas all subjects showed
nativelike performance in discriminating the tense vowel pair /u/ vs /y/. Results
of a keyword identification and rating task provided evidence that English listeners'
mapping of the German vowel to English vowel categories can be characterized as a
category goodness difference assimilation, and that the difference in category goodness
was more pronounced for the tense vowel pair than for the lax vowel pair. The results
failed to support the hypothesis that the acoustic structure of vowels consistently
favors auditory coding. Overall, the findings are compatible with existing data on
discrimination of cross-language consonant contrasts in natural speech and suggest
that linguistic experience shapes the discrimination of vowels and consonants as phonetic
segmental units in similar ways.