This study examined how discriminability and prototypicality of nonnative phones modulate the amplitude of the Mismatch Negativity (MMN) event-related brain potential. We hypothesized that if a frequently occurring (standard) stimulus is not prototypical to a listener, a weaker predictive memory trace will be formed and a smaller MMN will be generated for a phonetic deviant, regardless of the discriminability between the standard and deviant stimuli. The MMN amplitudes of Japanese speakers hearing the English vowels /æ/ and /ɑ/ as standard stimuli and /ʌ/ as a deviant stimulus in an oddball paradigm were measured. Although the English /æ/-/ʌ/ contrast was more discriminable than the English /ɑ/-/ʌ/ contrast for Japanese speakers, when Japanese speakers heard the /æ/ standard stimulus (i.e., less prototypical as Japanese /a/) and the /ʌ/ deviant stimulus, their MMN amplitude was smaller than the one elicited when they heard /ɑ/ as a standard stimulus (i.e., more prototypical as Japanese /a/) and /ʌ/ as a deviant stimulus. The prototypicality of the standard stimuli in listeners’ phonological representations modulates the MMN amplitude more robustly than does the discriminability between standard and deviant stimuli.

本研究检验了非母语音素的可辨别性和原型典型性如何调节不匹配负性 (MMN) 事件相关脑电位的振幅。我们假设，如果频繁出现的（标准）刺激对听众来说不是典型的，则无论标准刺激和异常刺激之间的可辨别性如何，都会形成较弱的预测记忆轨迹，并且将为语音异常生成较小的 MMN。测量了日本说话者听到英语元音 /æ/ 和 /ɑ/ 作为标准刺激和 /ʌ/ 作为古怪范式中的异常刺激的 MMN 振幅。虽然英语 /æ/-/ʌ/ 对比比英语 /ɑ/-/ʌ/ 对比对日本人来说更容易区分，当日本人听到 /æ/ 标准刺激（即，不太典型的日语 /a/) 和 /ʌ/ 异常刺激，他们的 MMN 幅度小于当他们听到 /ɑ/ 作为标准刺激（即更典型的日语 /a/）和 /ʌ/ 时引起的幅度作为异常刺激。与标准刺激和异常刺激之间的可辨别性相比，标准刺激在听者语音表征中的原型性对 MMN 振幅的调节更为稳健。