Researchers at the University of Chicago have found that we judge non-native speakers to be less believable, though not because of any bias against foreigners. Instead, they say, it's simply because we find these speakers harder to understand. (The study will appear in an upcoming issue of the Journal of Experimental Social Psychology.)
Shiri Lev-Ari and Boaz Keysar recorded three native English speakers, three speakers with mild accents (Polish, Turkish and Austrian-German) and three with heavy accents (Korean, Turkish and Italian) repeating statements like "a giraffe can go without water longer than a camel can." Speakers of American English then listened to 45 of these statements, 15 by each type of speaker. The listeners were told that the speakers were saying things that an experimenter had written, not expressing their own knowledge (in an attempt to rule out bias against the individual speaker), and asked whether each statement was true or false.
Statements read by people with accents—either mild or heavy—were less likely to be rated as true than those repeated by a native English speaker. When the exercise was repeated with the American English speakers being told that "the experiment is about the effect of the difficulty of understanding speakers' speech on the likelihood that their statements would be believed," thus warning them that an accent could affect credibility, the mildly accented speakers were rated just as truthful as the native speakers. Statements from individuals with heavy accents, though, were still more likely to be perceived as false.
The difference in credibility, Lev-Ari and Keysar say, occurs because an accent reduces something called "processing fluency." Instead of simply recognizing that we're having problems understanding the words, we interpret those words as being less believable. The researchers note:
These results have important implications for how people perceive non-native speakers of a language ... Accent might reduce the credibility of non-native job seekers, eyewitnesses, reporters or news anchors. ... Most likely, neither the native nor the non-native speakers are aware of this, making the difficulty of understanding accented speech an ever present reason for perceiving non-native speakers as less credible.
Perhaps this explains why I never believe the call center people from foreign lands when they tell me the cable guy is right around the corner and will be only a few minutes late.