用模拟人类语言习得机制的预训练,让大模型更高效学语言。
Language Acquisition Device in Large Language Models

- 在合成语言MP-STRUCT上做500步预预训练,模拟人类语言先天结构约束。
- 模型在词元效率上媲美强基准,且对不合理语言有更强抵抗力。
- 关键在于降低依赖歧义的功能标记,不只看表达能力,更要看可解析性。
大型语言模型(LLMs)的数据效率远低于人类。为缩小这一差距,已有研究提出在合成语言上进行预预训练(PPT),强调高度表达性的形式语言,如k-Shuffle Dyck。受语言习得装置(LAD)假说启发,我们提出基于LAD思想的PPT:在MP-STRUCT上预预训练,该形式语言通过MERGE、AGREE和MOVE编码层级组合、特征依赖与长距离移位。仅需500步的简短预预训练,即在词元效率上达到强形式语言基线水平,并赋予模型类似人类对结构不合理语言(如REVERSE)的抗性。分析简化版本发现,尽管MP-STRUCT CORE不可由C-RASP定义(限制Transformer表达力的形式边界),其表现仍优于k-Shuffle Dyck,挑战了此前认为有效PPT语言必须兼具层级表达力与电路可学习性的假设。结果表明,功能地标(减少依赖歧义)是关键驱动力,说明有效PPT设计不仅依赖表达力,还取决于依赖解析的可及性。
原文摘要 · Abstract (English)
Large Language Models (LLMs) remain substantially less data-efficient than humans. Pre-pretraining (PPT) on synthetic languages has been proposed to close this gap, with prior work emphasizing highly expressive formal languages such as $k$-Shuffle Dyck. Inspired by the Language Acquisition Device (LAD) hypothesis, which posits that innate constraints preemptively restrict the learner's hypothesis space to natural-language-like structure, we propose LAD-inspired PPT: pre-pretraining on MP-STRUCT, a formal language whose strings encode hierarchical composition, feature-based dependencies, and long-distance displacement via MERGE, AGREE, and MOVE. A brief 500-step PPT with MP-STRUCT matches strong formal-language baselines in token efficiency while additionally imparting a human-like resistance to structurally implausible languages (e.g., REVERSE). Analyzing simplified variants, we find that MP-STRUCT CORE outperforms $k$-Shuffle Dyck despite not being definable in C-RASP (a formal bound on transformer expressivity), challenging the prior hypothesis that effective PPT languages must be both hierarchically expressive and circuit-theoretically learnable. We show that functional landmarks, which reduce dependency resolution ambiguity, are a key driver, suggesting that effective PPT design depends not only on expressivity but also on the accessibility of dependency resolution.
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