用机器翻译文本预训练,能低成本提升低资源语言模型性能。
Scaling, Simplification, and Adaptation: Lessons from Pretraining on Machine-Translated Text
- 用机器翻译生成数据,配合模型缩放提升效果。
- 简化源文本反而降低模型对原生文本的泛化能力。
- 少量本地数据微调后,翻译数据预训练模型表现更优。
多数语言缺乏大规模单语预训练所需数据,形成‘数据壁垒’。多语言预训练受限于语言不平衡与‘多语言诅咒’。替代方案是使用机器翻译(MT)将高资源语言文本转换为低资源语言。本文研究三个问题:(1) MT数据在模型规模扩大时表现如何?(2) 对源语言文本进行简化(如用大模型简化英文)能否提升对原生文本的泛化能力?(3) 在少量原生文本上持续微调时,MT预训练模型适应能力如何?我们以英语翻译成印尼语和泰米尔语(两类形态差异大的低资源语言)为例,基于原始和大模型简化的英语数据,对GPT-2模型(124M–774M)进行预训练,并评估其在原生文本上的交叉熵损失、句法探针准确率及下游任务表现。结果表明:(1) MT预训练模型随规模扩大持续受益;(2) 源端简化损害模型在原生文本上的泛化能力;(3) 在少量原生数据微调后,MT预训练模型常优于纯原生数据训练模型,尤其在语法和通用任务上。但涉及文化敏感性的任务(如毒性检测)仍需更多原生数据支持。
原文摘要 · Abstract (English)
Most languages lack sufficient data for large-scale monolingual pretraining, creating a "data wall." Multilingual pretraining helps but is limited by language imbalance and the "curse of multilinguality." An alternative is to translate high-resource text with machine translation (MT), which raises three questions: (1) How does MT-derived data scale with model capacity? (2) Can source-side transformations (e.g., simplifying English with an LLM) improve generalization to native text? (3) How well do models pretrained on MT-derived data adapt when continually trained on limited native text? We investigate these questions by translating English into Indonesian and Tamil--two typologically distant, lower-resource languages--and pretraining GPT-2 models (124M-774M) on native or MT-derived corpora from raw and LLM-simplified English. We evaluate cross-entropy loss on native text, along with accuracy on syntactic probes and downstream tasks. Our results show that (1) MT-pretrained models benefit from scaling; (2) source-side simplification harms generalization to native text; and (3) adapting MT-pretrained models on native text often yields better performance than native-only models, even with less native data. However, tasks requiring cultural nuance (e.g., toxicity detection) demand more exposure to native data.
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