tokenization影响大模型认知,是理解语言意义的关键入口
Tokens, the oft-overlooked appetizer: Large language models, the distributional hypothesis, and meaning
- 揭示分词机制如何决定模型获取语言分布模式的能力
- 发现分词方式影响模型推理与潜在偏见传播,且难以通过对齐修复
- 适合关注大模型语义构建与语言认知本质的研究者
分词是当前生成式AI中基于Transformer的大语言模型(LLM)架构的必要组成部分,但其对模型认知的影响常被忽视。我们提出,大语言模型表明分布假设(DH)足以实现类人语言表现(尤其在推断性词汇能力方面),而词元中涌现出的人类可理解的语言单位及现有结构约束,推动对当前无语言依据的分词技术进行改进,特别是其作为传递人类语言显著分布模式至模型的载体和语义基本单元的角色。我们研究了BPE分词器、Hugging Face与tiktoken获取的现成模型词表,以及RoBERTa(large)模型各层中词元向量的信息。结果表明,现有分词方式制造次优语义单元,遮蔽模型对必要分布模式的访问,并可能成为偏见等不良内容的后门,而当前对齐手段未必能消除。此外,我们提供证据显示分词算法的目标函数影响大模型认知,尽管其看似与系统主智能隔离。最后讨论了对架构选择、意义建构、语言为思维之本,以及大模型认知的影响。
原文摘要 · Abstract (English)
Tokenization is a necessary component within the current architecture of many language mod-els, including the transformer-based large language models (LLMs) of Generative AI, yet its impact on the model's cognition is often overlooked. We argue that LLMs demonstrate that the Distributional Hypothesis (DH) is sufficient for reasonably human-like language performance (particularly with respect to inferential lexical competence), and that the emergence of human-meaningful linguistic units among tokens and current structural constraints motivate changes to existing, linguistically-agnostic tokenization techniques, particularly with respect to their roles as (1) vehicles for conveying salient distributional patterns from human language to the model and as (2) semantic primitives. We explore tokenizations from a BPE tokenizer; extant model vocabularies obtained from Hugging Face and tiktoken; and the information in exemplar token vectors as they move through the layers of a RoBERTa (large) model. Besides creating suboptimal semantic building blocks and obscuring the model's access to the necessary distributional patterns, we describe how tokens and pretraining can act as a backdoor for bias and other unwanted content, which current alignment practices may not remediate. Additionally, we relay evidence that the tokenization algorithm's objective function impacts the LLM's cognition, despite being arguably meaningfully insulated from the main system intelligence. Finally, we discuss implications for architectural choices, meaning construction, the primacy of language for thought, and LLM cognition. [First uploaded to arXiv in December, 2024.]
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