Neurocognitive study on the ongoing merge of Korean vowels /e/(/ㅔ/) and /ɛ/(/ㅐ/): Comparing MMNs of younger and older generations

Abstract

This study investigated the perceptual differences of the Korean vowels, /e/(/ㅔ/) and /ɛ/(/ㅐ/) between younger and older generations, comparing their behavioral and neural responses in order to examine the ongoing phenomenon of a merge of the two phonemes in Korean. The results of the behavioral discrimination task from 20 younger and 20 older generation participants in their 20s and 50s, respectively showed high accuracy rates with no significant differences between the two groups (Older: 91%, Younger: 94%). The reaction times were also similar to each other (Older: 330 ms, Younger: 360 ms). In the same vein, the results of the ERP experiment revealed that both groups showed neural sensitivity to the phonological difference between /e/(/ㅔ/) and /ɛ/(/ㅐ/), eliciting the MMN (Mismatch Negativity) in all conditions at the frontal and central electrodes. Nevertheless, and more importantly, the MMN amplitude was significantly enhanced in the older generation in comparison with the younger generation in the case of the standard /e/ with deviant /ɛ/, but not in the reversed condition of standard /ɛ/ with deviant /e/. The findings indicate that the older generation is more sensitive than the younger in distinguishing /ɛ/ from /e/ and that the two vowels merge to /e/, not /ɛ/. The results of the different MMN amplitudes properly demonstrate the perceptual differences between the two groups conforming to the findings of the previous studies on the production of /e/ and /ɛ/ merging to /e/. The findings of this study provide neurophysiological evidence for the ongoing merge of the two vowels in Korean.