Heuristic-Systematic Model (Chaiken, 1980)

The other dual-process theory of persuasion, running parallel to ELM. Systematic processing is effortful scrutiny of message content; heuristic processing applies low-effort rules of thumb ("experts are right", "length implies strength", "consensus implies truth"). Two ideas set it apart from elm: the least-effort principle (people process only as hard as they must) governed by the sufficiency principle — you keep processing until confidence crosses a threshold set by how much the outcome matters; and co-occurrence — both modes run simultaneously and can add, bias, or attenuate each other, rather than ELM's cleaner either/or router.

Transfer. The sufficiency threshold is the lever you actually move in awareness content. You cannot force a scroller into systematic processing, but you can raise their sufficiency bar — a stake, a surprising claim, a contested comment thread — so heuristics no longer feel like enough and they start reading for real. And when both modes co-run, a credibility heuristic (a real repo, a named author) doesn't just substitute for argument; it biases how favorably the argument that follows gets read. Stack the cue and the substance, not one or the other.

Kin: elm · cialdini-principles · processing-fluency · models · slop-is-a-context-deficit