Can Small Language Models Help Large Language Models Reason Better?: LM-Guided Chain-of-Thought
(2404.03414)Abstract
We introduce a novel framework, LM-Guided CoT, that leverages a lightweight (i.e., <1B) language model (LM) for guiding a black-box large (i.e., >10B) LM in reasoning tasks. Specifically, the lightweight LM first generates a rationale for each input instance. The Frozen large LM is then prompted to predict a task output based on the rationale generated by the lightweight LM. Our approach is resource-efficient in the sense that it only requires training the lightweight LM. We optimize the model through 1) knowledge distillation and 2) reinforcement learning from rationale-oriented and task-oriented reward signals. We assess our method with multi-hop extractive question answering (QA) benchmarks, HotpotQA, and 2WikiMultiHopQA. Experimental results show that our approach outperforms all baselines regarding answer prediction accuracy. We also find that reinforcement learning helps the model to produce higher-quality rationales with improved QA performance.
Overview
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The paper introduces a novel LM-Guided Chain-of-Thought (CoT) method to enhance reasoning in LLMs (LMs) by leveraging smaller LMs.
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This approach uses knowledge distillation and reinforcement learning to fine-tune a small LM for generating rationales that assist a larger LM in making predictions.
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Experimental results on the FLAN-T5 models using HotpotQA and 2WikiMultiHopQA datasets demonstrate the method's superiority in improving answer prediction accuracy and rationale quality.
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It discusses potential implications for advancing reasoning in LMs and identifies directions for future research, alongside acknowledging limitations and ethical considerations.
LM-Guided Chain-of-Thought: Enhancing Reasoning in LLMs with Smaller Counterparts
Introduction
The research presents an innovative approach to improving reasoning in LLMs (LMs) through the assistance of smaller, lightweight LMs. This strategy, termed LM-Guided Chain-of-Thought (CoT), involves a two-step process where a small LM generates a rationale for a given input, which then guides a larger, black-box LM to predict the task output. Unlike traditional methods that require extensive resources for training large models, this framework emphasizes efficiency by only necessitating the training of the smaller LM. Knowledge distillation and reinforcement learning are employed to fine-tune the model based on rationale-oriented and task-oriented rewards, demonstrating superior performance in multi-hop extractive question answering tasks.
Methodology
The framework comprises two main components:
- Rationale Distillation: Involves generating a rationale for each input instance using a small LM. This step utilizes knowledge distillation from a larger LM to bootstrap the smaller model's reasoning capabilities, focusing on generating high-quality rationales.
- Rationale Refinement: Builds upon the distilled model, applying reinforcement learning to optimize it based on a set of predefined rationale-specific aspects. These aspects include relevance, factuality, and coherence among others. The reinforcement learning component is designed to refine the quality of rationales further, thereby enhancing the overall reasoning process.
The experimental setup employs FLAN-T5 models of different sizes to serve the roles of small and large LMs, utilizing HotpotQA and 2WikiMultiHopQA datasets for evaluation. The method's success is attributed to its novel split between rationale generation and answer prediction, allowing for focused optimization of each part.
Results
The experimental results indicate several key findings:
- The LM-Guided CoT method surpasses baseline performances across multiple metrics, including answer prediction accuracy. This success showcases the efficacy of the proposed two-step reasoning process, especially when complemented with self-consistency decoding strategies.
- The application of reinforcement learning contributes to a noticeable improvement in the quality of generated rationales and, subsequently, question answering performance.
- The method reveals that selecting the highest-quality rationales does not unequivocally lead to better task outcomes, suggesting a complex relationship between rationale quality and effective reasoning in LMs.
Implications and Future Work
This research opens up new avenues for enhancing reasoning in LMs, particularly by leveraging smaller models to guide larger counterparts. The LM-Guided CoT framework proposes a resource-efficient method to improve large LM's reasoning capabilities without the need for extensive retraining. The findings underscore the significance of rationale quality in complex reasoning tasks and hint at potential strategies for further optimization. Future research directions could explore the generalizability of this approach to other forms of reasoning tasks, the integration of more sophisticated reinforcement learning techniques, and the exploration of other model combinations to enhance reasoning across diverse domains.
Limitations and Ethical Considerations
The study acknowledges limitations, including its focus on FLAN-T5 models and multi-hop QA tasks, which may not fully represent the framework's applicability across different settings and tasks. Future work is encouraged to test the framework's robustness and versatility across various reasoning demands and model architectures. Ethically, while the generated rationales were monitored for factual and respectful content within this study, deploying such models in real-world scenarios necessitates rigorous scrutiny to prevent the dissemination of inaccurate or harmful outputs.
Acknowledgments
The paper concludes by thanking reviewers for their constructive feedback, fostering an environment conducive to significant advancements in AI research.
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