数据聚合导致主观任务中大模型后验崩溃,应关注个体标注者。
Aggregation Artifacts in Subjective Tasks Collapse Large Language Models' Posteriors
- 用标注者级标签替代数据聚合,避免噪声干扰
- 少数标注者观点更符合大模型,且易被放大
- 提示工程依赖先验而非真正学习,需重新设计
上下文学习(ICL)已成为大语言模型执行自然语言任务的主要方法。预训练中获得的知识对这种少样本能力至关重要,为模型提供任务先验。然而,近期研究发现,ICL主要依赖于检索任务先验,而非真正“学习”任务。这一局限在情绪、道德等复杂主观领域尤为明显,先验显著影响后验预测。本文探讨数据集中聚合方式是否是导致此现象的原因:低一致性的异质标注合并可能引入标注伪影,形成提示中的有害噪声。我们通过量化测量大模型先验,评估其对特定标注者的后验偏倚。结果表明,聚合是主观任务建模中的混杂因素,建议聚焦个体标注者。但聚合无法解释全部ICL与顶尖性能间的差距,说明此类任务中还有其他因素发挥作用。通过严格分析标注者层级标签,我们发现少数标注者既能更好匹配大模型,又能使其观点进一步放大。
原文摘要 · Abstract (English)
In-context Learning (ICL) has become the primary method for performing natural language tasks with Large Language Models (LLMs). The knowledge acquired during pre-training is crucial for this few-shot capability, providing the model with task priors. However, recent studies have shown that ICL predominantly relies on retrieving task priors rather than "learning" to perform tasks. This limitation is particularly evident in complex subjective domains such as emotion and morality, where priors significantly influence posterior predictions. In this work, we examine whether this is the result of the aggregation used in corresponding datasets, where trying to combine low-agreement, disparate annotations might lead to annotation artifacts that create detrimental noise in the prompt. Moreover, we evaluate the posterior bias towards certain annotators by grounding our study in appropriate, quantitative measures of LLM priors. Our results indicate that aggregation is a confounding factor in the modeling of subjective tasks, and advocate focusing on modeling individuals instead. However, aggregation does not explain the entire gap between ICL and the state of the art, meaning other factors in such tasks also account for the observed phenomena. Finally, by rigorously studying annotator-level labels, we find that it is possible for minority annotators to both better align with LLMs and have their perspectives further amplified.
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