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arXiv:2309.12288cs.CL

The Reversal Curse: LLMs trained on "A is B" fail to learn "B is A"

Lukas Berglund, Meg Tong, Max Kaufmann, Mikita Balesni, Asa Cooper Stickland, Tomasz Korbak, Owain Evans

Abstract

We expose a surprising failure of generalization in auto-regressive large language models (LLMs). If a model is trained on a sentence of the form "A is B", it will not automatically generalize to the reverse direction "B is A". This is the Reversal Curse. For instance, if a model is trained on "Valentina Tereshkova was the first woman to travel to space", it will not automatically be able to answer the question, "Who was the first woman to travel to space?". Moreover, the likelihood of the correct answer ("Valentina Tershkova") will not be higher than for a random name. Thus, models do not generalize a prevalent pattern in their training set: if "A is B" occurs, "B is A" is more likely to occur. It is worth noting, however, that if "A is B" appears in-context, models can deduce the reverse relationship. We provide evidence for the Reversal Curse by finetuning GPT-3 and Llama-1 on fictitious statements such as "Uriah Hawthorne is the composer of Abyssal Melodies" and showing that they fail to correctly answer "Who composed Abyssal Melodies?". The Reversal Curse is robust across model sizes and model families and is not alleviated by data augmentation. We also evaluate ChatGPT (GPT-3.5 and GPT-4) on questions about real-world celebrities, such as "Who is Tom Cruise's mother? [A: Mary Lee Pfeiffer]" and the reverse "Who is Mary Lee Pfeiffer's son?". GPT-4 correctly answers questions like the former 79% of the time, compared to 33% for the latter. Code available at: https://github.com/lukasberglund/reversal_curse.

arXiv comments
21 pages, 11 figures
Journal reference
DOI
Subjects
cs.CLComputation and Language cs.AIArtificial Intelligence cs.LGMachine Learning

On Hacker News

Linked by 11 identifiable commenters in 11 comments across 10 threads, from Oct 2023 to Aug 2026. Found in 1 HN submission from Jun 2026 to Jun 2026. Open submission discussions.

Comments linking this paper, per year.

Discussed in comments10 threads

    • Its the tools. Sell those RSUs while they last. Most of these are 2026.... Frontier LLMs Still Struggle with Simple Reasoning Tasks - https://arxiv.org/abs/2507.07313 General365: Benchmarking General Reasoning in Large Language Models Across Diverse and Challenging Tasks…

      tcp_handshakerView on HNParent context

    • Probably an instance of: "The Reversal Curse: LLMs trained on "A is B" fail to learn "B is A" https://arxiv.org/abs/2309.12288

      kgeistView on HNParent context

  1. Learn Prolog Now (2006) 1 comment
  2. Mistral NeMo 1 comment
    • I don't have explanations but I can point you to one of the papers: https://arxiv.org/pdf/2309.12288 which calls it "the reversal curse" and does a bunch of experiments showing models that are successful at questions like "Who is Tom Cruise’s mother?" (Mary Lee Pfeiffer) will…

      michaeltView on HNParent context

    • I've written about the cognitive aspect the author talks about before: https://blog.jtoy.net/examining-concepts-through-different-f... https://blog.jtoy.net/on-the-wondrous-human-simulation-engin... https://arxiv.org/abs/2210.12068 The human brain has at least over 12 different…

      toisanjiView on HNParent context

  3. LLM: Transformer Is Linear 1 comment
    • Related papers: - https://arxiv.org/abs/2307.06962 - https://arxiv.org/abs/2309.12288 - https://arxiv.org/abs/2112.04426 - https://huggingface.co/papers/2405.14860

      williamtraskView on HNParent context

    • My take is when the model can't do the things that you would expect it to do if it were reasoning, and instead does the things that you would expect it to do if it were an approximate retrieval system with an enormous knowledge base. this is a good paper…

      sgt101View on HNParent context

  4. Greg Brockman quits OpenAI 1 comment
    • >Ilya claims the transformer architecture, with some modification for efficiency, is actually sufficient for AGI. I thought this guy was supposed to know what he's talking about? There was a paper that shows LLMs cannot generalise[0]. Anybody who's used ChatGPT can see there's…

      cedwsView on HNParent context

    • For anyone else interested, the paper he's referring to is "The Reversal Curse": https://arxiv.org/abs/2309.12288.

      sandkoanView on HNParent context

    • To add to this list of things LLMs don't understand: - Numbers (LLMs still can't do math and the ones that "can" are very brute forced and don't generalize) - Commutative properties (The (idk why anyone was surprised) "reversal curse": https://arxiv.org/abs/2309.12288)…

      godelskiView on HNParent context

    • > Numbers (LLMs still can't do math and the ones that "can" are very brute forced and don't generalize) These seem to generalize. https://arxiv.org/abs/2211.09066 https://arxiv.org/abs/2308.00304 > Commutative properties (The (idk why anyone was surprised) "reversal curse"…

      famouswafflesView on HNParent context

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