How credible is a non-native speaker? Prosody and surroundings

In order to evaluate the segmental and suprasegmental acoustic credibility correlates in the perception of native and non-native speech, a study was conducted on native and non-native speakers (NSs and NNS) of Italian. NNSs were chosen on the basis of L2 level of competence (A2, B1, C1 of CEFR), mother tongues (Chinese, Arabic, Japanese and Vietnamese) and degree of foreign accent (mild vs. strong). Four perceptive tests were carried out, two of them based on natural speech and the other two on modified speech. The corpus, formed by bizarre-but-true news read in Italian by all the involved subjects, was organized in form of radio news magazines and was used to conduct the tests. Native Italian listeners were asked to assess the truthfulness of each news item and its comprehensibility. Results revealed that the correlation between foreign accent and credibility is delivered by comprehensibility: poor comprehensibility generally lowers the credibility level of an utterance. When comprehensibility is high, a reduced tonal range and longer silent pauses, i.e. the suprasegmental features of the utterance, determine a significant increase of trustworthiness.