Sludge (behavioral science)

Sludge is the deliberate or accidental accumulation of friction in choice environments — excessive paperwork, hidden fees, confusing interfaces, and procedural delays — that discourages behaviors the system ostensibly encourages. Coined by behavioral economist Cass Sunstein as the inverse of nudge, sludge transforms the incentive architecture of institutions from a navigable landscape into a maze where the exit is technically available but practically inaccessible.

Sludge is not merely inefficiency. It is a structural feature of systems that benefit from the appearance of openness while operating through exclusion. The tax code's complexity, the health insurance enrollment maze, and the dark patterns of digital cancellation flows are not accidents of poor design. They are architectures that produce non-participation as surely as a well-designed nudge produces participation — and the two often coexist in the same system, nudging the favored behavior while sludging the disfavored one.