用算法检测威尔士媒体偏见，发现改革党被负面报道两倍于绿党。
Does Welsh media need a review? Detecting bias in Nation.Cymru's political reporting
- 分两阶段：先用RoBERTa识别偏见，再用大模型分析情感倾向。
- 改革党被负面描述次数是绿党的两倍，平均情绪更负（p<0.001）。
- 适合关注媒体公平性、政治传播研究者参考。
威尔士政治媒体饱受偏见指控。本文首次采用计算方法检验这些说法，聚焦主流新闻平台Nation.Cymru。研究构建两阶段NLP流程：（1）使用优化的RoBERTa模型高效检测偏见；（2）利用大语言模型对第一阶段标签进行目标指向的情感分类。主分析涵盖2022–2026年共15,583次政党提及，发现改革党（Reform UK）的偏见表述频率为绿党（Plaid Cymru）的两倍，且平均情感得分显著更低（p<0.001）。次级分析覆盖四党在新闻与评论文章中的表现，显示绿党获得明显更正面的框架描述。结果表明单一威尔士媒体存在可量化的差异化报道倾向，支持开展更广泛媒体审查。该两阶段框架成本低、可复现，适用于其他威尔士媒体或外部媒体生态的扩展研究。
原文摘要 · Abstract (English)
Wales' political landscape has been marked by growing accusations of bias in Welsh media. This paper takes the first computational step toward testing those claims by examining Nation.Cymru, a prominent Welsh political news outlet. I use a two-stage natural language processing (NLP) pipeline: (1) a robustly optimized BERT approach (RoBERTa) bias detector for efficient bias discovery and (2) a large language model (LLM) for target-attributed sentiment classification of bias labels from (1). A primary analysis of 15,583 party mentions across 2022-2026 news articles finds that Reform UK attracts biased framing at twice the rate of Plaid Cymru and over three times as negative in mean sentiment (p<0.001). A secondary analysis across four parties across both news and opinion articles shows that Plaid Cymru is the outlier, receiving markedly more favourable framing than any other party. These findings provide evidence of measurable differential framing in a single Welsh political media outlet, supporting calls for a broader review of Welsh media coverage. Furthermore, the two-stage pipeline offers a low-cost, replicable framework for extending this analysis to other Welsh outlets, as well as media ecosystems outside of Wales.
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