Researchers in Chicago have shown that people with a noticeable accent are considered less credible than those with no accent.
The stronger the accent, the less credible the speaker.
The researchers asked Americans to listen to native and non-native speakers of English making simple statements such as “A giraffe can go without water longer than a camel can,” and then judge how truthful they were.
To guard against simple prejudice, the listeners were told the information came from a prepared script and wasn’t based on the speaker’s own knowledge.
Even so, on a scale where 10 was most truthful, native English speakers got a score of 7.5, people with mild accents a score of 6.95 and people with heavy accents a score of 6.84.
The article is available here from the Journal of Experimental Social Psychology (subscription required).