“It’s not what you say, it’s how you say it” seems to have a lot of truth as research is showing a strong though probably unconscious effect that a person’s accent has on the listener. In an American study an accent which is very different from the listener’s was perceived to be less trustworthy and less reliable than one which was similar.  Possibly the difficulty for native Americans in understanding the unfamiliarly accented non-native speakers’ speech was misinterpreted as the speaker having less credibility rather than the true cause being the extra processing needed to gain understanding. Bestelmeyer’s  UK study supports this, as the Scottish participants reported similar findings when listening to Scottish speakers compared to American or English speakers. MRI scans showed that words spoken with familiar  accents are processed more quickly and effortlessly than other accents even when the language is native to all speakers. It is suggested that these processing difficulties may be the basis or origin of prejudice, as in one’s own accent identifying the ingroup, and other accents identifying outgroups.

Bestelmeyer et al. (2010) Society for Neuroscience. “Listeners’ Brains Respond More to Native Accent Speakers; Imaging Study Suggests Accents Are Subtle ‘Insider’ or ‘Outsider’ Signal to the Brain.” ScienceDaily, 18 November 2010.

Lev-Ari et al. (2010) Why don’t we believe non-native speakers? The influence of accent on credibility. Journal of Experimental Social Psychology, 2010; DOI: 10.1016/j.jesp.2010.05.025