Yale Attitude Change Approach (Hovland et al., 1950s)

The foundational empirical program (Hovland's Yale Communication Research group) that broke persuasion into "who says what to whom": source (credibility = expertise x trustworthiness; attractiveness), message (one- vs two-sided, argument order, fear appeals, explicit vs implicit conclusions), and audience (intelligence, prior attitude, self-esteem). It is a checklist of variables, not a single mechanism — later unified by ELM, which explains when each variable matters.

Its most useful discovery is the sleeper effect: a message from a low-credibility source gains persuasiveness over time, because memory of the content outlives memory of the discounting source. Two-sided messages (naming and rebutting the counter-argument) beat one-sided ones for informed or initially-opposed audiences.

Transfer. For agent-produced content the two-sided finding is the non-obvious one: naming your product's real weakness, or the strongest objection to your thesis, and then answering it, persuades a skeptical reader more than a clean brochure — it pre-empts their rebuttal and buys credibility. And the sleeper effect means an anonymous or thin-bylined piece isn't worthless; if the claim is sticky enough to be re-quoted, it survives detachment from its unimpressive origin. Design the quotable claim to travel without you.

Kin: elm · inoculation · rhetoric · models · being-seen-reliably