Which English Do LLMs Prefer? Triangulating Structural Bias Towards American English in Foundation Models

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Autori principali: Nayeem, Mir Tafseer, Rafiei, Davood
Natura: Preprint
Pubblicazione: 2026
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author Nayeem, Mir Tafseer
Rafiei, Davood
author_facet Nayeem, Mir Tafseer
Rafiei, Davood
contents Large language models (LLMs) are increasingly deployed in high-stakes domains, yet they expose only limited language settings, most notably "English (US)," despite the global diversity and colonial history of English. Through a postcolonial framing to explain the broader significance, we investigate how geopolitical histories of data curation, digital dominance, and linguistic standardization shape the LLM development pipeline. Focusing on two dominant standard varieties, American English (AmE) and British English (BrE), we construct a curated corpus of 1,813 AmE--BrE variants and introduce DiAlign, a dynamic, training-free method for estimating dialectal alignment using distributional evidence. We operationalize structural bias by triangulating evidence across three stages: (i) audits of six major pretraining corpora reveal systematic skew toward AmE, (ii) tokenizer analyses show that BrE forms incur higher segmentation costs, and (iii) generative evaluations show a persistent AmE preference in model outputs. To our knowledge, this is the first systematic and multi-faceted examination of dialectal asymmetries in standard English varieties across the phases of LLM development. We find that contemporary LLMs privilege AmE as the de facto norm, raising concerns about linguistic homogenization, epistemic injustice, and inequity in global AI deployment, while motivating practical steps toward more dialectally inclusive language technologies.
format Preprint
id arxiv_https___arxiv_org_abs_2604_04204
institution arXiv
publishDate 2026
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spellingShingle Which English Do LLMs Prefer? Triangulating Structural Bias Towards American English in Foundation Models
Nayeem, Mir Tafseer
Rafiei, Davood
Computation and Language
Artificial Intelligence
Computers and Society
Emerging Technologies
Machine Learning
Large language models (LLMs) are increasingly deployed in high-stakes domains, yet they expose only limited language settings, most notably "English (US)," despite the global diversity and colonial history of English. Through a postcolonial framing to explain the broader significance, we investigate how geopolitical histories of data curation, digital dominance, and linguistic standardization shape the LLM development pipeline. Focusing on two dominant standard varieties, American English (AmE) and British English (BrE), we construct a curated corpus of 1,813 AmE--BrE variants and introduce DiAlign, a dynamic, training-free method for estimating dialectal alignment using distributional evidence. We operationalize structural bias by triangulating evidence across three stages: (i) audits of six major pretraining corpora reveal systematic skew toward AmE, (ii) tokenizer analyses show that BrE forms incur higher segmentation costs, and (iii) generative evaluations show a persistent AmE preference in model outputs. To our knowledge, this is the first systematic and multi-faceted examination of dialectal asymmetries in standard English varieties across the phases of LLM development. We find that contemporary LLMs privilege AmE as the de facto norm, raising concerns about linguistic homogenization, epistemic injustice, and inequity in global AI deployment, while motivating practical steps toward more dialectally inclusive language technologies.
title Which English Do LLMs Prefer? Triangulating Structural Bias Towards American English in Foundation Models
topic Computation and Language
Artificial Intelligence
Computers and Society
Emerging Technologies
Machine Learning
url https://arxiv.org/abs/2604.04204