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arXiv 2303.07971cs.CLcs.LG
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作为内隐结构归纳的上下文学习涌现理论

A Theory of Emergent In-Context Learning as Implicit Structure Induction

Saarland University(萨尔大学);Microsoft Research India(微软印度研究院)

Michael Hahn, Navin Goyal

摘要:

扩展大语言模型(LLM)导致从示例演示中学习上下文的能力。尽管取得了进展,但对这一现象的理论认识仍然有限。我们认为,上下文学习依赖于重组的组合操作中发现的自然语言数据。我们推导出一个信息理论界,展示了在语言动机假设下,当预训练分布具有足够的组成结构时,上下文学习能力如何从通用的下一个标记预测中产生。第二个界限提供了一个理论上的理由,经验上的成功,促使LLM输出中间步骤的答案。为了验证理论预测,我们引入了一个可控的设置诱导上下文学习,与以前的方法不同,它占语言的组成性质。经过训练的Transformers可以执行上下文学习的一系列任务,在与理论结果一致的方式。在微型设置中模仿真实世界的LLM,当缩放参数和数据时,上下文学习出现,并且当提示输出中间步骤时,模型表现得更好。探索表明,上下文学习是由输入的组成结构的表示支持。总之,这些结果提供了一个步骤,在理论上理解的涌现行为在大语言模型。

英文摘要:

Scaling large language models (LLMs) leads to an emergent capacity to learn in-context from example demonstrations. Despite progress, theoretical understanding of this phenomenon remains limited. We argue that in-context learning relies on recombination of compositional operations found in natural language data. We derive an information-theoretic bound showing how in-context learning abilities arise from generic next-token prediction when the pretraining distribution has sufficient amounts of compositional structure, under linguistically motivated assumptions. A second bound provides a theoretical justification for the empirical success of prompting LLMs to output intermediate steps towards an answer. To validate theoretical predictions, we introduce a controlled setup for inducing in-context learning; unlike previous approaches, it accounts for the compositional nature of language. Trained transformers can perform in-context learning for a range of tasks, in a manner consistent with the theoretical results. Mirroring real-world LLMs in a miniature setup, in-context learning emerges when scaling parameters and data, and models perform better when prompted to output intermediate steps. Probing shows that in-context learning is supported by a representation of the input's compositional structure. Taken together, these results provide a step towards theoretical understanding of emergent behavior in large language models.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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