Multilingual Amnesia: On the Transferability of Unlearning in Multilingual LLMs

Fuente: arXiv
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Main Authors: Farashah, Alireza Dehghanpour, Khandelwal, Aditi, Fauchard, Marylou, Shi, Zhuan, Rostamzadeh, Negar, Farnadi, Golnoosh
Format: Preprint
Published: 2026
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author Farashah, Alireza Dehghanpour
Khandelwal, Aditi
Fauchard, Marylou
Shi, Zhuan
Rostamzadeh, Negar
Farnadi, Golnoosh
author_facet Farashah, Alireza Dehghanpour
Khandelwal, Aditi
Fauchard, Marylou
Shi, Zhuan
Rostamzadeh, Negar
Farnadi, Golnoosh
contents As multilingual large language models become more widely used, ensuring their safety and fairness across diverse linguistic contexts presents unique challenges. While existing research on machine unlearning has primarily focused on monolingual settings, typically English, multilingual environments introduce additional complexities due to cross-lingual knowledge transfer and biases embedded in both pretraining and fine-tuning data. In this work, we study multilingual unlearning using the Aya-Expanse 8B model under two settings: (1) data unlearning and (2) concept unlearning. We extend benchmarks for factual knowledge and stereotypes to ten languages through translation: English, French, Arabic, Japanese, Russian, Farsi, Korean, Hindi, Hebrew, and Indonesian. These languages span five language families and a wide range of resource levels. Our experiments show that unlearning in high-resource languages is generally more stable, with asymmetric transfer effects observed between typologically related languages. Furthermore, our analysis of linguistic distances indicates that syntactic similarity is the strongest predictor of cross-lingual unlearning behavior.
format Preprint
id arxiv_https___arxiv_org_abs_2601_05641
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Multilingual Amnesia: On the Transferability of Unlearning in Multilingual LLMs
Farashah, Alireza Dehghanpour
Khandelwal, Aditi
Fauchard, Marylou
Shi, Zhuan
Rostamzadeh, Negar
Farnadi, Golnoosh
Computation and Language
Machine Learning
As multilingual large language models become more widely used, ensuring their safety and fairness across diverse linguistic contexts presents unique challenges. While existing research on machine unlearning has primarily focused on monolingual settings, typically English, multilingual environments introduce additional complexities due to cross-lingual knowledge transfer and biases embedded in both pretraining and fine-tuning data. In this work, we study multilingual unlearning using the Aya-Expanse 8B model under two settings: (1) data unlearning and (2) concept unlearning. We extend benchmarks for factual knowledge and stereotypes to ten languages through translation: English, French, Arabic, Japanese, Russian, Farsi, Korean, Hindi, Hebrew, and Indonesian. These languages span five language families and a wide range of resource levels. Our experiments show that unlearning in high-resource languages is generally more stable, with asymmetric transfer effects observed between typologically related languages. Furthermore, our analysis of linguistic distances indicates that syntactic similarity is the strongest predictor of cross-lingual unlearning behavior.
title Multilingual Amnesia: On the Transferability of Unlearning in Multilingual LLMs
topic Computation and Language
Machine Learning
url https://arxiv.org/abs/2601.05641