Nonnative speech perception training using vowel subsets: effects of vowels in sets and order of training

K. Nishi and D. Kewley-Port (2007) trained Japanese listeners to perceive 9 American English monophthongs and showed that a protocol using all 9 vowels (fullset) produced better results than the one using only the 3 more difficult vowels (subset). The present study extended the target population to Koreans and examined whether protocols combining the 2 vowel sets would provide more effective training.

Three groups of 5 Korean listeners were trained on American English vowels for 9 days using one of the 3 protocols: fullset only, first 3 days on subset then 6 days on fullset, or first 6 days on fullset then 3 days on subset. Participants' performance was assessed by pre- and posttraining tests, as well as by a midtraining test.

(a) Fullset training was effective for Koreans as well as Japanese, (b) no advantage was found for the 2 combined protocols over the fullset-only protocol, and (c) sustained "nonimprovement" was observed for training using one of the combined protocols.

In using subsets for training on American English vowels, care should be taken not only in the selection of subset vowels but also in the training orders of subsets.