SemEval-2026 Task 10: PsyCoMark – Psycholinguistic Conspiracy Marker Extraction and Detection
Summary
PsyCoMark is a SemEval-2026 shared task on recognizing conspiracy-theory language in ordinary online conversation. Most prior benchmarks target a few fixed claims or topics, such as COVID-19 on Twitter. To counter this, the organizers built a Reddit corpus of submission statements, the short comments in which posters explain why shared media fits a subreddit. These come from 226 communities, ranging from openly conspiratorial forums to general news, TV and politics, so models cannot rely on topic cues. Crowdworkers on Prolific labeled each text as conspiracy, not conspiracy or can't tell. They also marked spans for five markers derived from evolutionary psychology: Actor, Action, Effect, Victim and Evidence.
The task has two parts: span extraction of markers (Subtask 1) and document-level detection (Subtask 2). Scoring combined standard metrics with a Bayesian hierarchical analysis of subreddit difficulty. Extraction proved much harder than detection. The best systems paired fine-tuned transformers with LLM components, data augmentation and marker-aware modeling. Few teams exploited the strong link between markers and labels, which leaves room for joint approaches.
Key points
- Dataset size: 5,354 annotated documents (4,720 unique) from 226 subreddits, labeled by 138 native English speakers. They contain 27,891 marker spans. Documents split into 1,925 "conspiracy", 2,457 "not conspiracy" and 972 "can't tell".
- Annotator agreement: Krippendorff's α was 0.58 for binary labels, but unitizing α was only 0.15 for marker spans.
- Markers and labels: Texts containing all five markers had the highest conspiracy rate. However, the particular combination of markers mattered more than their raw count. Actor and Action were the most frequent markers and co-occurred most often.
- Topic is a weak signal: Conspiracy labels were mixed even within conspiracy-focused subreddits. Polarized, viewpoint-diverse communities such as TheMotte and Israel_Palestine were the hardest to predict.
- Release and top system: The data are on Zenodo under CC-BY, without raw text; a rehydration script is provided, and 20% was held out as a private test set. The winning system (Zheng and Yang, 2026) combined retrieval-augmented prompts, keyword-based LLM filtering and weighted classification.
Institutions
Cite
@inproceedings{samory2026semeval,
title = {{SemEval-2026 Task 10: PsyCoMark – Psycholinguistic Conspiracy Marker Extraction and Detection}},
author = {Samory, Mattia and Soldner, Felix and Batzdorfer, Veronika},
booktitle = {Proceedings of the 20th International Workshop on Semantic Evaluation (2026)},
year = {2026},
doi = {10.18653/v1/2026.semeval-1.444},
url = {https://doi.org/10.18653/v1/2026.semeval-1.444}
}References
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