Bertie Vidgen
Also known as Bertram Vidgen
Bertie Vidgen is a researcher whose work spans online-hate detection, language-model safety and evaluation of AI agents. At Oxford, he researched Islamophobic hate speech among followers of UK political parties on Twitter and coauthored a dynamically generated dataset for hate detection. He coauthored XSTest, a test for exaggerated safety refusals, and PRISM, a cross-country human-feedback dataset that won NeurIPS's 2024 Best Paper award in the Datasets and Benchmarks track. In 2025, he wrote about human-annotated data for RAG agents at Contextual AI and coauthored Mercor's APEX benchmark for economically valuable knowledge work. In September 2026, he coauthored APEX-Agents 1.1; as of October 2026, he is a researcher on Mercor's research team and first author of APEX-Agents.
Timeline
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2015–2019
DPhil research on online hate
He holds a BA in History and Politics from Warwick and an MA in Ideology and Discourse Analysis from Essex. From October 2015 to June 2019, he studies for a DPhil at Oxford's Internet Institute, researching Islamophobic hate speech among followers of UK political parties on Twitter.
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October 2019–December 2023
Research Associate at Oxford
From October 2019 to December 2023, he is a Research Associate at the Oxford Internet Institute. He studies hate speech in news and social media using machine learning, natural language processing and statistical modelling. He also works as a post-doctoral researcher within the Alan Turing Institute's Public Policy Programme.
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2021
Learning from the Worst
In 2021, he coauthors Learning from the Worst, a hate-detection dataset with 40,000 entries generated and labelled by trained annotators over four rounds. The paper reports that models trained on later rounds perform better on test sets and are harder for annotators to trick.
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2024
XSTest safety benchmark
In 2024, he coauthors XSTest, a test suite for exaggerated safety behaviours in large language models. It pairs 250 safe prompts that well-calibrated models should comply with and 200 unsafe prompts they should refuse.
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2024
NeurIPS Best Paper for PRISM
In 2024, he coauthors PRISM, a dataset linking the stated preferences of 1,500 participants in 75 countries to fine-grained feedback in 8,011 live conversations with 21 LLMs. NeurIPS names it Best Paper in the Datasets and Benchmarks track.
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March 2025
Human data for RAG agents
In March 2025, he describes how Contextual AI's Data team creates human-annotated datasets to specialize and evaluate RAG agents for customer use cases.
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October 2025
Mercor's APEX benchmark
In October 2025, he coauthors Mercor's AI Productivity Index (APEX), a benchmark that evaluates AI models on economically valuable knowledge work.
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As of October 2026
Researcher at Mercor
As of October 2026, he is a researcher on Mercor's Research team and first author of APEX-Agents. In September 2026, he coauthors APEX-Agents 1.1, a benchmark that tests models on real-world work across investment banking, management consulting and corporate law.
Career
- NowMercorResearcher
- 2019–2023University of OxfordResearch Associate
Education
- 2019University of OxfordDPhil
- University of WarwickBA in History and Politics
- University of EssexMA in Ideology and Discourse Analysis
Sources and credits
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- OII | Bertram Vidgen
- Learning from the Worst: Dynamically Generated Datasets to Improve Online Hate Detection
- XSTest: A Test Suite for Identifying Exaggerated Safety Behaviours in Large Language Models
- NeurIPS 2024 Awards
- The PRISM Alignment Dataset: What Participatory, Representative and Individualised Human Feedback Reveals About the Subjective and Multicultural Alignment of Large Language Models
- Building better agents: The critical role of human-annotated data
- Introducing APEX: The AI Productivity Index
- Why Mercor is building a research team
- Introducing APEX-Agents 1.1


