Thomas H. Costello

Researcher who was first author on both halves of a single connected research program on AI and conspiracy belief: the 2024 Science study showing a tailored, three-round AI dialogue can durably reduce belief in a person's own targeted conspiracy (and, to a smaller degree, in unrelated ones), and the 2026 follow-up showing the identical technique works just as well run in reverse, to instill false conspiracy belief — though only where the model is not instructed to argue truthfully, a condition the 2026 paper's own v3 revision moved into its title [hedge added 2026-10-16 by the scheduled audit; see the correction recorded on claim-2026-symmetry-result-answers-a-question-2024-paper-posed]. Gordon Pennycook and David G. Rand are co-authors on both papers; the continuity between the two studies — including the 2024 paper naming, as its own next question, exactly the true/false-symmetry test the 2026 paper went on to run — runs through Costello as the thread connecting them.

References

• claim-tailored-ai-dialogue-durably-reduced-conspiracy-belief · claim-conspiracy-belief-was-the-paradigm-case-of-evidence-immunity · claim-llm-conspiracy-persuasion-is-dual-use
• claim-2024-conspiracy-spillover-was-a-measured-8-percent-drop-not-a-reasoning-claim · claim-costello-2024-central-route-mechanism-is-a-hedged-inference · claim-2026-dual-use-paper-found-mirror-image-spillover-on-gcbs · claim-2026-symmetry-result-answers-a-question-2024-paper-posed
• claim-costello-2024-science-paper-carries-live-expression-of-concern · claim-nyhan-independently-reproduced-2024-costello-debunking-finding
• Capture: 10-inbox/raw/2026-10-13-does-the-costellopennycookrand-2024-finding-that-a-tailored.md

Updates

• 2026-10-17: A Science Expression of Concern (dated by Retraction Watch to 2026-06-11) flags the 2024 paper for screening-criteria inconsistencies the authors self-reported between manuscript and analysis pipeline; political scientist Brendan Nyhan independently reproduced the 2024 finding in two experiments at Dartmouth, the nearest independent corroboration anywhere in this lineage. Neither discharges the single-source cap on the 2026 preprint — the EOC doesn't touch its data, and Nyhan replicated the 2024 debunking finding, not the 2026 symmetry result. (claim-costello-2024-science-paper-carries-live-expression-of-concern, claim-nyhan-independently-reproduced-2024-costello-debunking-finding)