Why do accents carry prestige, and what is accent bias?

Because judgements about accents are judgements about the people who use them, transferred onto the sound — there is nothing in the phonetics of one accent that makes it more correct, clearer or more intelligent than another.

What linguistics establishes. All accents are rule-governed, systematic and equally capable of expressing anything. No accent is a degraded version of another, and the accent treated as "standard" in any country is simply the one spoken by the group that held power when the standard was codified.

In Britain, Received Pronunciation was never spoken by more than a small minority, and its prestige derives from its association with public schools, the historic BBC and the professions — not from any property of the sound.

What the research on bias finds, and it is substantial:

Accent affects judgements of intelligence, competence, trustworthiness and even guilt. Studies using matched-guise methods — the same speaker, same words, different accent — find consistently different ratings.

The effects reach real outcomes, including employment, where studies find accent affecting shortlisting and perceived suitability, and courtroom research finding effects on perceived credibility.

Hierarchies are consistent within a country. In Britain, surveys repeatedly find RP and some regional accents rated highly while urban working-class accents — Birmingham and some London and Liverpool accents in particular — are rated lowest, and these rankings have been stable over decades.

Accent bias operates even where people disavow it, and even among speakers of the disfavoured accent.

"Processing fluency" is a partial but insufficient explanation. Unfamiliar accents take marginally more effort to process, which is perceived as less credible — but this cannot explain why familiar accents are rated low, which points to social evaluation rather than comprehension.

Where it sits legally. Accent is not itself a protected characteristic in most systems, but accent discrimination can amount to indirect discrimination by race or national origin, and has been argued on that basis.

What has changed: broadcasting has diversified substantially, and accent bias is increasingly recognised as a legitimate workplace equality issue rather than a matter of taste.