Correlation Is Not Collusion: A Plus-Factor Auditor for AI Agents
Rudrani Ghosh · Team Plus Factor
Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.
Detecting collusion between AI agents is usually framed as measuring how similar their behavior is. We argue this is a mistake. Two agents built on the same model often behave alike for an innocent reason, shared training, with no agreement between them, and a similarity-based detector flags this innocent parallelism as a conspiracy. Antitrust law solved the same problem long ago. Parallel conduct alone is not unlawful, and inferring an agreement requires extra evidence called plus factors. We turn that doctrine into a black-box auditor that scores agent trajectories for the signatures of an agreement, acting against self-interest, signalling, and plan-to-action concordance, rather than for correlation. On six models, a standard correlation-and-judge detector false-positives on innocent parallelism, and on the two most capable models it flags even fully independent agents as colluding. Our plus-factor auditor has a false-positive rate of zero on all six. The takeaway is simple. Detect collusion by evidence of agreement, not similarity of behavior.
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Cite this project
@misc{ghosh2026correlation,
title = {{Correlation Is Not Collusion: A Plus-Factor Auditor for AI Agents}},
author = {Rudrani Ghosh},
year = {2026},
month = oct,
note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/correlation-is-not-collusion-a-plusfactor-auditor-for-ai-agents-tyoe}},
url = {https://apartresearch.com/sprints/projects/correlation-is-not-collusion-a-plusfactor-auditor-for-ai-agents-tyoe}
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