This paper explores whether young vs. old Koreans’ vowel insertion after word-final English and French postvocalic plosives has changed or not. For this purpose, we conducted a perception experiment wherein 40 Koreans who were born before 1960 and another 40 Koreans who were born after 1989 were recruited with 20 male and 20 female subjects in each group. The results show that the release of plosives and the voicing of unreleased plosives are key variables for vowel insertion in both age groups. In addition, our young Koreans have no significant difference in vowel insertion after word-final English and French plosives, regardless of whether the plosives are released or unreleased, regardless of whether they are voiceless or voiced and regardless of whether they are preceded by the tense vowel [a I], as in English stimuli, or by the non-tense vowel [a], as in the French stimuli. On the other hand, our old Koreans have differences in vowel insertion after the non-native plosives in the examined contexts, depending on whether the plosives are English or French.
Based on the results, we propose that vowel insertion in accordance with the plosive release and the voicing of unreleased plosives in the two groups is accounted for by Korean syllable structure with generational differences made by how two effects – the plosive voicing effect and the vowel-tenseness effect – are involved. We also propose that no significant difference in vowel insertion after word-final English and French plosives in the young group is a case of contact-induced borrowing change resulting from the English/French contact differences over time in Korean society.