fluency effect, one manifestation of which is our tendency to assume that how easily a message is processed is a mark of its truthfulness. The effort required to understand an accented utterance means that the same fact is judged as less credible when uttered by an accented speaker, compared with a native speaker. This remains true even if the accented speaker is merely passing on a message from a native speaker.
Shiri Lev-Ari and Boaz Keysar recruited 9 speakers to utter 45 trivia facts, such as 'A giraffe can go without water longer than a camel'. Three of the speakers were native (American) English speakers; three had mild foreign accents and originated from Poland, Turkey or Austria/Germany; and three had strong accents and were from either Korea, Turkey or Italy.
Twenty-eight undergrad participants rated the veracity of each of the spoken facts (which speakers uttered which facts varied from participant to participant in a balanced design). Crucially, participants were led to believe that the study was really about using intuition to judge facts. Also, it was made clear to them that the facts had been penned by the researchers - that the speakers were merely acting as messengers. To drill home this idea, the researchers also had the participants go through the charade of themselves uttering a few facts, ostensibly to be presented to other participants.
On a 0-14cm scale from 'definitely false' at one end to 'definitely true' at the other, the participants rated facts spoken by mild and heavily accented speakers as less believable than facts uttered by native English speakers (the mean ratings were 6.95, 6.84 and 7.59, respectively - a statistically significant difference).
What if participants are made aware that the difficulty they have processing a foreign accent could be interfering with their judgements? A second study with another 27 undergrads tested this very idea. It was similar to the first but this time participants were told the explicit aim of the study. Now, facts spoken by a speaker with a mild accent were judged to be just as credible as facts spoken by a native English speaker. However, facts spoken by a heavily accented speaker were still judged to be less true. It seems we can override our bias for assuming easily processed utterances are more truthful - but only up to a point. Also, it's worth remembering that in real life, prejudice towards foreign speakers is likely to augment the effects observed here.
'These results have important implications for how people perceive non-native speakers of a language, particularly as mobility increases in the modern world, leading millions of people to be non-native speakers of the language they use daily,' the researchers concluded. 'Accent might reduce the credibility of non-native job seekers, eye-witnesses, reporters or news anchors.'
Lev-Ari, S., and Keysar, B. (2010). Why don't we believe non-native speakers? The influence of accent on credibility. Journal of Experimental Social Psychology, 46 (6), 1093-1096 DOI: 10.1016/j.jesp.2010.05.025
Link to related open-access feature article in The Psychologist magazine [Hyunjin Song and Norbert Schwarz describe some fascinating findings on how fluency affects judgement, choice and processing style].