Illusion of control — Langer (1975); REPLICATION-FLAGGED: classic Study 2 failed to replicate in Kühberger et al. (1995, four experiments, none successful)

Claim: Illusion of control is the tendency to overestimate one's ability to influence outcomes that are substantially determined by factors outside one's control — fuelling the belief that constant tweaking is moving the needle.

For new-site owners: changing the headline, the hero image, the button colour — feels like influencing the outcome, even when the actual outcome (Google indexing, trust accrual, ranking) is governed by factors the owner cannot move quickly (see the sister brief, Mueller (May 28, 2021 SEO office hours) on new-site ranking instability — "we don't have a lot of signals for that new content yet… we have to make assumptions").

Source: Langer, E. J. (1975). "The Illusion of Control." Journal of Personality and Social Psychology 32(2):311–328.

Confidence: Replication-flagged. The general direction (people overestimate their influence on chance-determined outcomes) is Industry-consensus. The specific Langer Study 2 effect has repeatedly failed to replicate — Kühberger, Perner, Schulte & Leingruber (1995) ran four experiments and none reproduced the original finding. Treat Langer's effect size as Directional, not Verified.

Caveat: This is one of the two replication-flagged effects in the brief (the other is loss-aversion magnitude — Loss aversion — Kahneman & Tversky (1979) prospect theory; REPLICATION-FLAGGED: Gal & Rucker (2018) challenged universal 2:1 claim; Walasek/Mullett/Stewart meta-analytic re-examinations find coefficient ≈1.3 (or near 1 under symmetric conditions); Kahneman conceded "not a law of human nature"). Do not cite "illusion of control" as a quantitatively settled effect; cite it as the direction of a real cognitive tendency whose magnitude in any given context is unestablished.