Quantifying and alleviating political bias in language models

Abstract

Current large-scale language models can be politically biased as a result of the data they are trained on, potentially causing serious problems when they are deployed in real-world settings. In this paper, we first describe metrics for measuring political bias in GPT-2 generation, and discuss several interesting takeaways: 1) The generation of vanilla GPT-2 model is mostly liberal-leaning, 2) Such political bias depends on the sensitive attributes mentioned in the context, and 3) Priming the generation with a explicit political identifier, the extent of political bias is imbalanced (between liberal and conservative).We then propose a reinforcement learning (RL) framework for mitigating such political biases in generated text: By using rewards from word embeddings or a classifier, our RL framework guides debiased generation without having access to the training data or requiring the model to be retrained. In empirical experiments on three attributes sensitive to political bias (gender, location, and topic), our methods reduced bias according to both our metrics and human evaluation, while maintaining readability and semantic coherence.