Source credibility
Who delivers a message shapes how persuasive it is.
What it means
The degree to which a communicator is perceived as believable, which powerfully moderates persuasion and rests mainly on two dimensions: expertise (does the source know?) and trustworthiness (will the source tell the truth?). High-credibility sources persuade more, especially via the peripheral route when audiences are not closely scrutinizing arguments, while trustworthiness is boosted when a source argues against its own apparent interest. Credibility effects can fade over time (the sleeper effect) and depend on perceived similarity and attractiveness as well. It matters as a primary lever in advertising, public health, and political messaging.
Examples
A drug claim from a physician moves people more than the identical claim from an anonymous blogger.
A wine shop that tells you the £9 bottle beats the £30 one earns your trust precisely because the advice cuts against its own takings.
Weeks after an advert, people recall the claim but not that it came from the company selling the product — the discount they applied to the source has worn off.
First described in Hovland & Weiss (1951); Yale attitude-change program.