用视觉汉字结构替代可训练嵌入,模型仍能高效推理。
Emergent Semantics Beyond Token Embeddings: Transformer LMs with Frozen Visual Unicode Representations
- 用预计算的汉字视觉结构做固定嵌入
- 在MMLU上表现优于可训练嵌入模型
- 适合研究语义涌现与模型架构本质
理解大语言模型中语义表征的位置对可解释性和架构创新至关重要。主流观点认为可训练输入嵌入是基础的‘意义向量’。本文挑战这一观点:构建完全冻结嵌入层的Transformer模型,其向量由Unicode字形的视觉结构生成,非数据驱动,且全程固定。该方法兼容任何分词器,包括我们提出的新型以Unicode为中心的分词器,确保文本全覆盖。尽管无可训练、语义初始化的嵌入,模型仍能收敛、生成连贯文本,并在MMLU推理基准上显著超越具有可训练嵌入的同构模型。我们归因于传统模型中嵌入层需同时学习结构与语义特征所导致的‘表征干扰’。结果表明,高层语义并非嵌入固有属性,而是变压器组合架构与数据规模共同作用下的涌现特性。这重新定义了嵌入的角色——从意义容器变为结构基元。所有代码与模型已开源,以促进后续研究。
原文摘要 · Abstract (English)
Understanding the locus of semantic representation in large language models (LLMs) is crucial for interpretability and architectural innovation. The dominant paradigm posits that trainable input embeddings serve as foundational "meaning vectors." This paper challenges that view. We construct Transformer models where the embedding layer is entirely frozen, with vectors derived not from data, but from the visual structure of Unicode glyphs. These non-semantic, precomputed visual embeddings are fixed throughout training. Our method is compatible with any tokenizer, including a novel Unicode-centric tokenizer we introduce to ensure universal text coverage. Despite the absence of trainable, semantically initialized embeddings, our models converge, generate coherent text, and, critically, outperform architecturally identical models with trainable embeddings on the MMLU reasoning benchmark. We attribute this to "representational interference" in conventional models, where the embedding layer is burdened with learning both structural and semantic features. Our results indicate that high-level semantics are not inherent to input embeddings but are an emergent property of the Transformer's compositional architecture and data scale. This reframes the role of embeddings from meaning containers to structural primitives. We release all code and models to foster further research.
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