Effect sizes shrink on replication

Updated: 2026.01.16 13D ago 4 sources
In a coordinated attempt to replicate 100 psychology studies, only about 36% reproduced statistically significant results and the average effect size was roughly half the original. The project used standardized protocols and open materials to reduce garden‑of‑forking‑paths and showed that headline findings are often inflated. — It warns media and policymakers to demand replication and preregistration before building policy or public narratives on single, striking studies.

Sources

Tweet by @degenrolf
@degenrolf 2026.01.16 82% relevant
The tweet reports that an influential consumer‑behavior finding failed elaborate replication attempts — a direct instance of the broader pattern that many social‑psychology effects shrink or fail to replicate, as summarized by the existing idea.
Psychology’s Greatest Misses (Part 1/3)
Josh Zlatkus 2026.01.07 88% relevant
The authors survey widely‑believed psychological claims and show they fail robust replication; this aligns with documented empirical findings that replications often halve original effect sizes and that single‑study claims are inflated.
The Collapse of Ego Depletion - by Michael Inzlicht
2026.01.05 90% relevant
Inzlicht’s essay documents the very phenomenon summarized by the existing idea—initial, influential findings (ego depletion) that later fail large‑scale replications and whose effects shrink when retested—naming actors (Roy Baumeister, the replication community) and describing the methodological and cultural drivers that produce inflated early effects.
PSYCHOLOGY. Estimating the reproducibility of psychological science - PubMed
2015.10.07 100% relevant
Open Science Collaboration (Science, 2015, 349: aac4716) mass‑replication results (significance rate ~36%; effect‑size shrinkage).
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