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Advanced Hallucination Mitigation Techniques in LLMs RAG, knowledge editing, contrastive decoding, self-refinement, uncertainty-aware beamsearch 0 like January 15, 2025Share this postLast Updated on January 15, 2025 by Editorial TeamAuthor(s): Mohit Sewak, Ph.D. Originally published on Towards AI. Advanced Hallucination Mitigation Techniques in LLMs: Beyond RAG to a World of RichesStuck in the RAG rut? Break free and discover other innovative and powerful techniques like knowledge editing, contrastive decoding, self-refinement, uncertainty-aware beam search, and many more.Unlocking the Riches: Mitigating Hallucinations in LLMs.Related Articles (Recommended PreReads)Hallucinations in LLMs: Can You Even Measure the Problem?Unmasking the Surprising Diversity of AI HallucinationsHallucination is like Autism, it has types and spectrum Prepare to be surprised by the Wide Spectrum of AI HallucinationsIntroduction: The Problem with HallucinationsPicture this: Youre asking your Large Language Model (LLM) to summarize the history of tea. With confidence, it replies, Tea was invented by a squirrel in 2500 BC to stay awake during winter hibernation. Wait, what? Unless squirrels were ancient alchemists, thats a bona fide hallucination a moment where the LLM concocts something so wild it might make Hollywood writers jealous.Hallucinations in LLMs arent just about quirky trivia gone rogue. In serious contexts like healthcare, finance, or legal advice they can lead to misinformation with real-world consequences. The irony? These hallucinations emerge from the same power that makes LLMs so good: their ability to predict coherent text by analyzing vast patterns in data.Now, you might say, But RAG (Retrieval-Augmented Generation) has got this under control, right? Sure, RAG has been the knight in shining armor, retrieving external facts to ground responses. But relying solely on RAG is like patching a leaky boat with duct tape it works, but only up to a point. Its time we explore newer, shinier tools to tame the hallucination beast.In this article, well venture beyond RAG into the uncharted territories of advanced mitigation techniques. From Knowledge Editing (the surgeons scalpel) to Contrastive Decoding (the ultimate fact-checker), each method is a superhero in the making. Buckle up, grab your masala chai, and lets dive into a world where hallucinations meet their match.Section 1: RAG A Safety Net with HolesRetrieval-Augmented Generation, or RAG, is the dependable workhorse of hallucination mitigation. Its charm lies in its simplicity: fetch relevant information from external sources (like knowledge bases or vector databases) and hand it over to the LLM as context for text generation. Think of it as giving your LLM a cheat sheet before the big test.But heres the catch: RAG isnt infallible. For starters, its effectiveness hinges on the quality of the retrieved data. If your vector database is filled with outdated or irrelevant information, the LLM might as well be guessing answers from a magic 8-ball. Worse, RAG doesnt inherently verify its sources, leaving room for sneaky hallucinations to creep in.Then theres the issue of dependency. By relying solely on external retrieval, we risk turning the LLM into an overconfident intern who parrots whatever they read online hardly the paragon of reliability were aiming for. Plus, the process of retrieving and integrating external data can slow things down, making RAG less practical for real-time applications.But dont get me wrong; RAG isnt obsolete. Its the dependable friend you call when youre in a pinch. However, as the AI landscape evolves, we need to pair it with more sophisticated tools. Luckily, the next-gen techniques were about to explore promise just that.Pro Tip: While RAG works wonders in knowledge-heavy domains, always double-check the quality of your retrieval sources. Garbage in, garbage out!RAG: A valiant effort, but not always enough.Section 2: Knowledge Editing: The Surgeons ScalpelImagine youre editing an encyclopedia, and you find an entry claiming Shakespeare was a software developer. Instead of rewriting the whole article, youd fix just that line. Thats what Knowledge Editing does for LLMs. Its a precision tool that allows us to update specific facts within the models parameters without disrupting its broader capabilities.How It WorksKnowledge Editing techniques like ROME (Rank-One Model Editing) and MEMIT (Model Editing via Memory) identify the specific neural connections responsible for a factual association. Then, like a neurosurgeon with a steady hand, they tweak those connections to replace incorrect information with the truth. MEMIT goes a step further by storing these edits in a memory module, ensuring the model remembers the corrections over time.For example, if your model claims the Earth is flat (thanks, internet conspiracies), you can use ROME to pinpoint the weight matrices responsible for that knowledge and adjust them to say, The Earth is an oblate spheroid. Voil, your model is now a geography nerd.Why Its CoolUnlike traditional fine-tuning, which retrains the entire model and risks breaking unrelated functionalities, Knowledge Editing is surgical. It minimizes collateral damage, preserves the models performance on other tasks, and saves computational resources.The Laugh TrackLets picture ROME and MEMIT as doctors in a sitcom:ROME: The straight-laced, no-nonsense surgeon who gets the job done in one clean swoop.MEMIT: The quirky neurologist who insists on adding a memory bank for every patient. Together, they keep your LLM in top shape.Rome and MEMIT performing a neural operation precision at its finest.Section 3: Contrastive Decoding: The Ultimate Fact-CheckerImagine youre at a party, and two friends start debating who invented the telephone. One says its Alexander Graham Bell; the other insists it was Thomas Edison. As the mediator, you compare their arguments, fact-check their claims, and declare the winner. That, in a nutshell, is what contrastive decoding does but for LLMs.What Is Contrastive Decoding?Contrastive decoding pits two models against each other during text generation. One is the primary LLM (the know-it-all), and the other is a contrastive model (the skeptic). For every token the LLM generates, the contrastive model raises its eyebrow and goes, Are you sure about that? The final output is a blend of probabilities that favor tokens deemed factual and coherent by both models.The math behind it boils down to tweaking probabilities based on a weighted difference between the primary model and the contrastive model. Think of it as having a grammar teacher who double-checks your work before you hit submit.Why It WorksLLMs can sometimes generate tokens that seem plausible but lack factual grounding. By using a smaller, less hallucination-prone model for contrast, this method curbs the primary models overconfidence. Its like having a devils advocate who questions everything, ensuring only reliable tokens make the cut.Real-Life AnalogyPicture a talkative parrot that loves to ad-lib stories. Next to it, you place a parrot trainer who knows the facts. Every time the parrot squawks nonsense, the trainer nudges it back on track. The result? A parrot that sounds not just entertaining but also accurate.The Humor FactorLets imagine the models as siblings in a family dinner debate:The LLM: Im pretty sure Napoleon won the Battle of Waterloo.The Contrastive Model: Bruh, thats not even close. Google it!Together, they settle on the truth and avoid embarrassing the family.Contrastive decoding where every word gets a fair trial.Section 4: Self-Refinement: The Models Self-Help JourneyIf youve ever written a first draft and then gone back to refine it, congratulations! Youve already practiced self-refinement, one of the most exciting techniques in hallucination mitigation. Here, the model essentially becomes its own editor, reviewing and improving its initial output.How It WorksSelf-refinement operates in a loop:The LLM generates a response.It evaluates its own output for inconsistencies or hallucinations.Based on that evaluation, it revises and improves the response.This process mirrors how humans refine their thoughts before speaking. For example, if the model initially says, The moon is made of cheese, self-refinement kicks in to correct it to, The moon consists of rock and dust.Why Its BrilliantSelf-refinement empowers the model to use its internal knowledge more effectively. By iterating on its output, it learns to identify flaws and generate more accurate text. Its like giving the model a journal where it can write, reflect, and grow wiser.The Self-Help AnalogyImagine an LLM attending a motivational workshop:Speaker: Every hallucination is a stepping stone to the truth!LLM: furiously taking notesBy the end of the session, the model has not only improved its answers but also gained a newfound sense of purpose.Fun Fact: Self-refinement aligns with the concept of reinforcement learning from human feedback (RLHF). Its like having a personal trainer who claps every time you do a perfect push-up.Self-refinement: When an LLM turns inward for better answers.Section 5: Uncertainty-Aware Beam Search: Playing It SafeIf LLMs were explorers, uncertainty-aware beam search would be their map and compass. This method helps models steer clear of risky terrain aka hallucinations by favoring safer, more reliable paths during text generation.The BasicsBeam search is a decoding strategy where multiple sequences (or beams) are explored simultaneously. In uncertainty-aware beam search, each beam is assigned a confidence score. Beams with high uncertainty likely to lead to hallucinations are pruned, leaving only the trustworthy ones.Why Its SafeThis method acts as the cautious driver who double-checks directions before making a turn. By avoiding paths with high uncertainty, it reduces the chances of generating wild, unsupported claims. Sure, it might sacrifice some creativity, but when accuracy is the goal, caution wins the day.Analogy TimeThink of beam search as a group of hikers exploring a forest. Uncertainty-aware beam search is the guide who says, That path looks sketchy; lets not go there. Thanks to this guide, the group avoids getting lost or in the case of LLMs, generating bizarre answers.Pro Tip: Use uncertainty-aware beam search when deploying LLMs in critical domains like healthcare or law. Its better to be safe than sorry!Uncertainty-aware beam search navigating safely through the forest of text.Section 6: Iterative Querying and Reasoning: Detective WorkIf Sherlock Holmes were an LLM, hed use iterative querying and reasoning to solve every mystery. This technique enables models to interrogate themselves repeatedly, poking holes in their own logic until only the truth remains. Its the ultimate self-skepticism toolkit for LLMs, ensuring theyre not just saying something plausible but also correct.How It WorksThe LLM generates an initial response.It asks itself follow-up questions or attempts alternative explanations to test the validity of its own output.Based on this internal cross-examination, it refines the response to make it more accurate and consistent.This method mirrors how detectives build their cases. They gather clues, test theories, and refine conclusions until the truth comes to light. For example, if the model generates, Unicorns are real, iterative querying might prompt it to ask, Whats the scientific evidence for unicorns? forcing it to confront the fallacy.Why Its CleverIterative querying and reasoning exploit the LLMs internal knowledge and reasoning capabilities. By engaging in self-dialogue, the model becomes more critical of its own outputs, reducing the chances of hallucination. Its like having an inner Watson double-checking Sherlocks deductions.Detective HumorImagine the LLM as a trench-coat-wearing sleuth:LLM: Elementary, my dear user. The capital of Brazil is Buenos Aires.Watson (aka Iterative Querying): Hold on, old chap. Isnt it Braslia?Cue a dramatic pause, followed by a corrected response. Mystery solved!Real-World ApplicationsThis technique shines in scenarios requiring logical reasoning or evidence-based answers. From academic research to medical diagnosis, iterative querying ensures outputs are less prone to fanciful detours.Iterative querying where LLMs play detective to find the truth.Section 7: Decoding Strategy Optimization: The Compass for TruthDecoding strategies are the unsung heroes of text generation. They determine how an LLM picks its words, and when optimized, they can steer the model away from hallucinations. Think of them as the compass guiding the LLM through the vast terrain of possible outputs.What Are Decoding Strategies?Decoding is the process of selecting the next token in a sequence. Strategies like greedy decoding, beam search, and nucleus sampling dictate how this selection happens. Optimized decoding strategies tweak these processes to balance fluency, diversity, and factual accuracy.Key TechniquesContrastive DecodingWeve already covered this one a tug-of-war between two models that ensures factuality.Factual Nucleus SamplingStandard nucleus sampling selects tokens from the top percentile of probabilities. Factual nucleus sampling adds a twist: it prioritizes tokens backed by factual evidence. Its like curating a guest list where only the well-informed are invited.Monte Carlo DropoutThis technique generates multiple outputs by applying dropout at inference time, then selects the most reliable one. Picture a robot running simulations and picking the most sensible outcome.Why It WorksDecoding strategies operate directly at the generation level, so they dont require retraining or external resources. Theyre lightweight, flexible, and powerful tools for improving output quality.Humor BreakImagine an LLM navigating a treacherous mountain trail of possible outputs:LLM: Ill take this shortcut wait, no, it leads to The moon is cheese! Lets try the main path.Thanks to decoding optimization, it always finds the safest route.Decoding optimization charting the safest route to factuality.Section 8: Combining Forces: The Avengers of Hallucination MitigationWhat happens when you bring together self-refinement, contrastive decoding, iterative querying, and beam search? You get an elite squad of techniques ready to obliterate hallucinations. Think of it as assembling the Avengers for the AI world, where each technique brings unique strengths to the table.How It WorksCombining techniques means leveraging their complementary strengths. For example:Contrastive Decoding + RAG: Retrieve external knowledge to fill gaps, then use contrastive decoding to verify and refine the response.Self-Refinement + Uncertainty-Aware Beam Search: Let the model refine its outputs while steering clear of uncertain paths.Iterative Querying + Knowledge Editing: Combine detective-like self-interrogation with precise fact updates for ironclad reliability.The Movie PitchPicture this:RAG: The resourceful genius with a database of knowledge.Contrastive Decoding: The sharp-tongued fact-checker.Self-Refinement: The introspective philosopher.Iterative Querying: The inquisitive detective.Together, theyre a blockbuster team saving the world from misinformation.Why Its the FutureNo single method can eliminate hallucinations entirely. By combining forces, we can cover each techniques blind spots, creating a system thats robust, reliable, and ready for real-world deployment.The Avengers of Hallucination Mitigation stronger together.Conclusion: Towards a World of RichesAs we wrap up this wild ride through the realm of hallucination mitigation, one thing is clear: tackling hallucinations in LLMs isnt a one-size-fits-all endeavor. Its more like assembling a toolbox, where each method from RAGs trusty retrieval skills to the philosophical self-refinement plays a vital role in ensuring our models are not just eloquent but also accurate.Mitigating hallucinations is about balance. While some techniques, like Knowledge Editing, offer precision, others, like Iterative Querying, provide introspection. Together, they form a symphony of strategies that make LLMs safer, smarter, and more reliable.But lets not forget the human element in this journey. Whether its the developers refining these methods, researchers exploring uncharted territories, or users like us questioning the answers we receive, the fight against hallucination is a collaborative effort. After all, the goal isnt just to make models less wrong its to make them tools we can trust.So, next time you sip your cardamom tea and marvel at the wonders of generative AI, remember the heroes working behind the scenes those clever algorithms ensuring your LLM doesnt claim that squirrels invented tea. Heres to a future where hallucinations are less of a nuisance and more of a curiosity we can laugh about, all while unlocking the true potential of AI.References & Further ReadingKnowledge EditingMeng, K., Bau, D., Andonian, A., & Belinkov, Y. (2022). Locating and editing factual associations in GPT. Advances in Neural Information Processing Systems, 35, 1735917372.Meng, K., Sharma, A. S., Andonian, A., Belinkov, Y., & Bau, D. (2022). Mass-editing memory in a transformer. arXiv preprint arXiv:2210.07229.Contrastive DecodingLi, X. L., Holtzman, A., Fried, D., Liang, P., Eisner, J., Hashimoto, T., & Lewis, M. (2022). Contrastive decoding: Open-ended text generation as optimization. arXiv preprint arXiv:2210.15097.Self-RefinementNiu, M., Li, H., Shi, J., Haddadi, H., & Mo, F. (2024). Mitigating Hallucinations in Large Language Models via Self-Refinement-Enhanced Knowledge Retrieval. arXiv preprint arXiv:2405.06545.Uncertainty-Aware Beam SearchZeng, H., Zhi, Z., Liu, J., & Wei, B. (2021). Improving paragraph-level question generation with extended answer network and uncertainty-aware beam search. Information Sciences, 571, 5064.Iterative Querying and ReasoningLi, W., Wu, W., Chen, M., Liu, J., Xiao, X., & Wu, H. (2022). Faithfulness in natural language generation: A systematic survey of analysis, evaluation and optimization methods. arXiv preprint arXiv:2203.05227.Qi, P., Lin, X., Mehr, L., Wang, Z., & Manning, C. D. (2019). Answering complex open-domain questions through iterative query generation. arXiv preprint arXiv:1910.07000.General TechniquesHuang, L., Yu, W., Ma, W., Zhong, W., Feng, Z., Wang, H., & Liu, T. (2023). A survey on hallucination in large language models: Principles, taxonomy, challenges, and open questions. ACM Transactions on Information Systems.Perkovi, G., Drobnjak, A., & Botiki, I. (2024, May). Hallucinations in llms: Understanding and addressing challenges. In 2024 47th MIPRO ICT and Electronics Convention (MIPRO) (pp. 20842088). IEEE.Mishra, A., Asai, A., Balachandran, V., Wang, Y., Neubig, G., Tsvetkov, Y., & Hajishirzi, H. (2024). Fine-grained hallucination detection and editing for language models. arXiv preprint arXiv:2401.06855.Disclaimers and DisclosuresThis article combines the theoretical insights of leading researchers with practical examples, and offers my opinionated exploration of AIs ethical dilemmas, and may not represent the views or claims of my present or past organizations and their products or my other associations.Use of AI Assistance: In preparation for this article, AI assistance has been used for generating/ refining the images, and for styling/ linguistic enhancements of parts of content.Follow me on: | Medium | LinkedIn | SubStack | X | YouTube |Join thousands of data leaders on the AI newsletter. Join over 80,000 subscribers and keep up to date with the latest developments in AI. From research to projects and ideas. If you are building an AI startup, an AI-related product, or a service, we invite you to consider becoming asponsor. 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