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Interaction of Lexical Frequency on the Perception of Accented Speech

Natacha Moreno, M.S., CCC-SLP


Many factors have the potential to influence accentedness, or the degree to which a non-native speaker of a language is perceived to have a foreign accent.  Included are the age in which the speaker began learning the second language, the length of time the individual has lived in the L2 (second language) environment, and even the motivation of the speaker to refine their accent.  Ultimately, it’s the speaker's level of mastery of the sounds, intonation patterns, syntax, semantics, and morphology of the target language that play a significant role in accentedness.  However, speaker-specific features are not the only factors influencing the perception of foreign accented speech.   The listener’s language background and familiarity with an accent must also be taken into account, as well as the listener’s hearing acuity.  Even the listening environment – quiet versus noisy - plays a role. 


An additional element to consider when discussing the listener’s perception of accent is the level, or complexity of the spoken language being used.  At the word level, this relates to  the listener’s comprehension of  the vocabulary being used, but it may also include  a listener’s exposure to a word, also known as lexical frequency.   For instance, when a non-native speaker of English uses a high frequency word such as “heart,” does the listener perceive an equal degree of accent as when the same speaker employs a low frequency word like “valve?”


In native speech, lexical frequency has already been shown to affect speech perception and language processing.  Based on exemplar models of speech perception, “The more frequently a word occurs in the language, the more often a listener will hear it being spoken, which will in turn lead to encoding more exemplars of the word in memory.” (Winters, Levi, and Pisoni, 2007) The more exemplars of the word in memory the more quickly and easy it is to process by the listener.  In contrast, less frequently occurring words require more processing, as the listener must rely more heavily on the acoustic-phonetic information (acoustic aspects of speech sounds) in the speech signal, given there are fewer exemplars in memory of low frequency words.  For this reason, researchers have begun to question whether the reliance on acoustic-phonetic information in the processing of low frequency words would lead native English speakers to perceive those words as more accented in non-native speech than high frequency words. 


In 2007, researchers Winters, Levi, and Pisoni performed a perceptual ratings study wherein 60 native English listeners were presented with recorded speech samples of both native speakers of English (11 monolingual) and non-native speakers (13 bilingual).   Each subject listened to recordings of a combined total of 576 low, medium, and high frequency English words, all in CVC form – consonsont-vowel-consonant.  The listeners then used the following rating scale ranging from 0 (“no foreign accent/native speaker of English”) to 6 (“most foreign accent”) to judge the degree of accentedness of the production. 


Results of this study revealed that lexical frequency indeed affects the perception of foreign accent in spoken words.  For non-native speakers, low frequency words were rated as more accented than both medium and high frequency words; and no significant difference between the medium and high frequency words was found.  


The outcome of this study may have implications for non-native professionals that employ domain specific vocabulary as a function of their job.  It calls into question the relationship between the degree of accented speech and the accuracy with which a listener deciphers an utterance, and consequently the effectiveness of the communicative exchange.


Levi, Susannah V., Stephen J. Winters, and David B. Pisoni. “Speaker-Independent Factors Affecting the Perception of Foreign Accent in a Second Language.” The Journal of the Acoustical Society of America 121.4 (2007): 2327–2338. Print.


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