David Mortensen

@davidrmortensen.bsky.social

I make colorless green GPUs sleep brrriously. Computational phonology, morphology, language change models, speech/language technologies (especially for people with disabilities).

Can LLMs accurately aggregate information over long, information-dense texts? Not yet… We introduce Oolong, a dataset of simple-to-verify information aggregation questions over long inputs. No model achieves >50% accuracy at 128K on Oolong!

Performance of a sweep of models on Oolong-synth and Oolong-real. Performance decreases with increasing context length, sometimes steeply.

🚨New paper: Reward Models (RMs) are used to align LLMs, but can they be steered toward user-specific value/style preferences? With EVALUESTEER, we find even the best RMs we tested exhibit their own value/style biases, and are unable to align with a user >25% of the time. 🧵

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🚨New Paper: LLM developers aim to align models with values like helpfulness or harmlessness. But when these conflict, which values do models choose to support? We introduce ConflictScope, a fully-automated evaluation pipeline that reveals how models rank values under conflict. (📷 xkcd)

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🔈When LLMs solve tasks with a mid-to-low resource input or target language, their output quality is poor. We know that. But can we put our finger on what breaks inside the LLM? We introduce the 💥 translation barrier hypothesis 💥 for failed multilingual generation with LLMs. arxiv.org/abs/2506.22724

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When it comes to text prediction, where does one LM outperform another? If you've ever worked on LM evals, you know this question is a lot more complex than it seems. In our new #acl2025 paper, we developed a method to find fine-grained differences between LMs: 🧵1/9

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RL boosts LLM reasoning—but why stop at math & code? 🤔 Meet Nemotron-CrossThink—a method to scale RL-based self-learning across law, physics, social science & more. 🔥Resulting in a model that reasons broadly, adapts dynamically, & uses 28% fewer tokens for correct answers! 🧵↓

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On my way to #NAACL2025 where I'll give a keynote at the noisy text workshop (WNUT), presenting some of the challenges & methods for dialect NLP + also discussing dialect speakers' perspectives! 🗨️ Beyond “noisy” text: How (and why) to process dialect data 🗓️ Saturday, May 3, 9:30–10:30

Excited to announce our #NAACL2025 Oral paper! 🎉✨ We carried out the largest systematic study so far to map the links between upstream choices, intrinsic bias, and downstream zero-shot performance across 131 CLIP Vision-language encoders, 26 datasets, and 55 architectures!

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When interacting with ChatGPT, have you wondered if they would ever "lie" to you? We found that under pressure, LLMs often choose deception. Our new #NAACL2025 paper, "AI-LIEDAR ," reveals models were truthful less than 50% of the time when faced with utility-truthfulness conflicts! 🤯 1/

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1/🚨 𝗡𝗲𝘄 𝗽𝗮𝗽𝗲𝗿 𝗮𝗹𝗲𝗿𝘁 🚨 RAG systems excel on academic benchmarks - but are they robust to variations in linguistic style? We find RAG systems are brittle. Small shifts in phrasing trigger cascading errors, driven by the complexity of the RAG pipeline 🧵

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THIS IS HUGE! Researchers at McMaster University have discovered a NEW peptide antibiotic that targets a broad range of disease-causing bacteria INCLUDING those RESISTANT to existing antibiotics. This discovery marks the first potential new class of antibiotics in NEARLY 30 YEARS. 🧪🧵⬇️

I’ve been thinking about this reading from Isaiah 58 since I heard it at the Ash Wednesday service today. “Is not this the fast that I choose: to loose the bonds of injustice, to undo the thongs of the yoke, to let the oppressed go free, and to break every yoke?

🚨New Breakthrough in Tip-of-the-Tongue (TOT) Retrieval Research! We address data limitations and offer a fresh evaluation method for these complex queries. Curious how TREC TOT track test queries are created? Check out this thread 🧵 and our paper 📄: arxiv.org/abs/2502.17776

Tip of the Tongue Query Elicitation for Simulated Evaluation

Tip-of-the-tongue (TOT) search occurs when a user struggles to recall a specific identifier, such as a document title. While common, existing search systems often fail to effectively support TOT scena...

arxiv.org