Improving language models fine-tuning with representation consistency targets

Fine-tuning contextualized representations learned by pre-trained language models has become a standard practice in the NLP field. However, pre-trained representations are prone to degradation (also known as representation collapse) during fine-tuning, which leads to instability, suboptimal performance, and weak generalization. In this paper, we propose a novel fine-tuning method that avoids representation collapse during fine-tuning by discouraging undesirable changes in the representations. We show that our approach matches or exceeds the performance of the existing regularization-based fine-tuning methods across 13 language understanding tasks (GLUE benchmark and six additional datasets). We also demonstrate its effectiveness in low-data settings and robustness to label perturbation. Furthermore, we extend previous studies of representation collapse and propose several metrics to quantify it. Using these metrics and previously proposed experiments, we show that our approach obtains significant improvements in retaining the expressive power of representations.