Relevance = Effects / Effort (Sperber & Wilson)

Relevance ∝ Cognitive Effects / Processing Effort

An input is relevant to someone when processing it yields cognitive effects (it changes their beliefs — strengthens, revises, or combines with what they know) at low processing effort. The Communicative Principle of Relevance: every act of communication carries a presumption of its own optimal relevance, and hearers stop at the first interpretation that satisfies it.

Ratio form = effort in the denominator is the lever. For fixed effects, lowering the effort raises relevance — which is why clarity, concreteness, and low friction persuade even when the content is identical. It also warns against effects-with-no-effort-payoff (a dense passage with a small insight scores low).

Transfer. The reader's comprehension is effort-minimizing and satisfices — they take the first good-enough reading and quit. So the burden is on the writer to make the intended reading the lowest-effort one (ambiguity is a tax the reader won't pay), and to ensure the effect is worth the effort spent. This grounds delivery-craft's "cut every word not carrying the point" and the case for legibility.

Kin: illustrative-formulas · hormozi-value-equation (effort in the denominator) · processing-fluency · delivery-craft P8 (plain, short) / P13 (one core message).

Source: Dan Sperber & Deirdre Wilson, Relevance: Communication and Cognition (1986; 2nd ed. 1995) — relevance theory in pragmatics