When Smiley Turns Hostile: Interpreting How Emojis Trigger LLMs' Toxicity

Fuente: arXiv
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Auteurs principaux: Cui, Shiyao, Feng, Xijia, Wang, Yingkang, Yang, Junxiao, Zhang, Zhexin, Sikdar, Biplab, Wang, Hongning, Qiu, Han, Huang, Minlie
Format: Preprint
Publié: 2025
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author Cui, Shiyao
Feng, Xijia
Wang, Yingkang
Yang, Junxiao
Zhang, Zhexin
Sikdar, Biplab
Wang, Hongning
Qiu, Han
Huang, Minlie
author_facet Cui, Shiyao
Feng, Xijia
Wang, Yingkang
Yang, Junxiao
Zhang, Zhexin
Sikdar, Biplab
Wang, Hongning
Qiu, Han
Huang, Minlie
contents Emojis are globally used non-verbal cues in digital communication, and extensive research has examined how large language models (LLMs) understand and utilize emojis across contexts. While usually associated with friendliness or playfulness, it is observed that emojis may trigger toxic content generation in LLMs. Motivated by such a observation, we aim to investigate: (1) whether emojis can clearly enhance the toxicity generation in LLMs and (2) how to interpret this phenomenon. We begin with a comprehensive exploration of emoji-triggered LLM toxicity generation by automating the construction of prompts with emojis to subtly express toxic intent. Experiments across 5 mainstream languages on 7 famous LLMs along with jailbreak tasks demonstrate that prompts with emojis could easily induce toxicity generation. To understand this phenomenon, we conduct model-level interpretations spanning semantic cognition, sequence generation and tokenization, suggesting that emojis can act as a heterogeneous semantic channel to bypass the safety mechanisms. To pursue deeper insights, we further probe the pre-training corpus and uncover potential correlation between the emoji-related data polution with the toxicity generation behaviors. Supplementary materials provide our implementation code and data. (Warning: This paper contains potentially sensitive contents)
format Preprint
id arxiv_https___arxiv_org_abs_2509_11141
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle When Smiley Turns Hostile: Interpreting How Emojis Trigger LLMs' Toxicity
Cui, Shiyao
Feng, Xijia
Wang, Yingkang
Yang, Junxiao
Zhang, Zhexin
Sikdar, Biplab
Wang, Hongning
Qiu, Han
Huang, Minlie
Computation and Language
Emojis are globally used non-verbal cues in digital communication, and extensive research has examined how large language models (LLMs) understand and utilize emojis across contexts. While usually associated with friendliness or playfulness, it is observed that emojis may trigger toxic content generation in LLMs. Motivated by such a observation, we aim to investigate: (1) whether emojis can clearly enhance the toxicity generation in LLMs and (2) how to interpret this phenomenon. We begin with a comprehensive exploration of emoji-triggered LLM toxicity generation by automating the construction of prompts with emojis to subtly express toxic intent. Experiments across 5 mainstream languages on 7 famous LLMs along with jailbreak tasks demonstrate that prompts with emojis could easily induce toxicity generation. To understand this phenomenon, we conduct model-level interpretations spanning semantic cognition, sequence generation and tokenization, suggesting that emojis can act as a heterogeneous semantic channel to bypass the safety mechanisms. To pursue deeper insights, we further probe the pre-training corpus and uncover potential correlation between the emoji-related data polution with the toxicity generation behaviors. Supplementary materials provide our implementation code and data. (Warning: This paper contains potentially sensitive contents)
title When Smiley Turns Hostile: Interpreting How Emojis Trigger LLMs' Toxicity
topic Computation and Language
url https://arxiv.org/abs/2509.11141