On the Cross-lingual Transferability of Monolingual Representations
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/2020.acl-main.421.pdf
Summary
Why can multilingual BERT apply a task learned only from English labels to other languages? The usual explanation credits subwords shared across languages, which act as anchors, and joint pre-training, which spreads this alignment into deep cross-lingual representations. Artetxe, Ruder and Yogatama test this account with a method that breaks all of these assumptions. They pre-train a BERT-style model on English alone. They then adapt it to a second language by learning new token embeddings from that language's monolingual corpus and separate vocabulary, keeping the transformer body frozen. Optional extras are language-specific position embeddings, noised fine-tuning and adapters. After English fine-tuning, the English embeddings are swapped for the new ones. This approach, MonoTrans, matches jointly trained multilingual models on XNLI, MLDoc and PAWS-X. With adapters it also approaches mBERT on XQuAD, a new question answering benchmark the authors release. The results show that shared vocabulary and joint training are unnecessary and that monolingual models learn partly language-independent abstractions. They also show that released models can gain new languages without access to their original training data.
Key points
- Baselines: MonoTrans was compared with JointMulti, a BERT trained jointly on 15 XNLI languages with vocabularies of 32k, 64k, 100k and 200k subwords. Other baselines were JointPair, an English-plus-one bilingual BERT, and CLWE, which uses skip-gram embeddings mapped to English with VecMap in orthogonal mode under an English BERT.
- Tokenization: All models use the SentencePiece unigram model. The authors contend that how many subwords each language actually gets to use is a key consideration for multilingual models.
- XQuAD: The new dataset has 240 paragraphs and 1190 question-answer pairs from SQuAD v1.1. Professional translators rendered them into ten languages, and the dataset is public at github.com/deepmind/xquad.
- CLWE results: CLWE is competitive only on the small, easy MLDoc task. It falls clearly behind on XNLI and XQuAD.
- Probing: Representations were learned in non-English languages and transferred into English, then probed with WiC, SCWS and the Marvin and Linzen syntactic evaluation. Semantic knowledge transfers fairly well, with WiC scores comparable to English-trained models. Syntactic abstractions show larger gaps.
Cited by
- ARBERT & MARBERT: Deep Bidirectional Transformers for Arabic
- Do All Languages Cost the Same? Tokenization in the Era of Commercial Language Models
- MEGA: Multilingual Evaluation of Generative AI
- The Belebele Benchmark: a Parallel Reading Comprehension Dataset in 122 Language Variants
- On the Opportunities and Risks of Foundation Models
- PaLI: A Jointly-Scaled Multilingual Language-Image Model
- InfoXLM: An Information-Theoretic Framework for Cross-Lingual Language Model Pre-Training
- Rethinking embedding coupling in pre-trained language models
- TyDi QA: A Benchmark for Information-Seeking Question Answering in Typologically Diverse Languages
- Emerging Cross-lingual Structure in Pretrained Language Models
- XTREME: A Massively Multilingual Multi-task Benchmark for Evaluating Cross-lingual Generalization
- MuRIL: Multilingual Representations for Indian Languages
- ChatGPT Beyond English: Towards a Comprehensive Evaluation of Large Language Models in Multilingual Learning
- From Zero to Hero: On the Limitations of Zero-Shot Language Transfer with Multilingual Transformers
- MLQA: Evaluating Cross-lingual Extractive Question Answering
- Crosslingual Generalization through Multitask Finetuning
- MAD-X: An Adapter-Based Framework for Multi-Task Cross-Lingual Transfer
- Lifting the Curse of Multilinguality by Pre-training Modular Transformers
- XCOPA: A Multilingual Dataset for Causal Commonsense Reasoning
- XTREME-R: Towards More Challenging and Nuanced Multilingual Evaluation
- How Good is Your Tokenizer? On the Monolingual Performance of Multilingual Language Models
- Beyond the Imitation Game: Quantifying and extrapolating the capabilities of language models
- Aya Model: An Instruction Finetuned Open-Access Multilingual Language Model
- Probing Pretrained Language Models for Lexical Semantics
- Do Llamas Work in English? On the Latent Language of Multilingual Transformers
- Are All Languages Created Equal in Multilingual BERT?
- mGTE: Generalized Long-Context Text Representation and Reranking Models for Multilingual Text Retrieval
Cite
@inproceedings{artetxe2020cross,
title = {{On the Cross-lingual Transferability of Monolingual Representations}},
author = {Artetxe, Mikel and Ruder, Sebastian and Yogatama, Dani},
booktitle = {Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics},
year = {2020},
doi = {10.18653/v1/2020.acl-main.421},
eprint = {1910.11856},
archivePrefix = {arXiv},
url = {https://doi.org/10.18653/v1/2020.acl-main.421}
}References
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