Impacts of Continued Legal Pre-Training and IFT on LLMs' Latent Representations of Human-Defined Legal Concepts

This paper aims to offer AI & Law researchers and practitioners a more detailed understanding of whether and how continued pre-training and instruction fine-tuning (IFT) of large language models (LLMs) on legal corpora increases their utilization of human-defined legal concepts when developing global contextual representations of input sequences. We compared three models: Mistral 7B, SaulLM-7B-Base (Mistral 7B with continued pre-training on legal corpora), and SaulLM-7B-Instruct (with further IFT). This preliminary assessment examined 7 distinct text sequences from recent AI & Law literature, each containing a human-defined legal concept. We first compared the proportions of total attention the models allocated to subsets of tokens representing the legal concepts. We then visualized patterns of raw attention score alterations, evaluating whether legal training introduced novel attention patterns corresponding to structures of human legal knowledge. This inquiry revealed that (1) the impact of legal training was unevenly distributed across the various human-defined legal concepts, and (2) the contextual representations of legal knowledge learned during legal training did not coincide with structures of human-defined legal concepts. We conclude with suggestions for further investigation into the dynamics of legal LLM training.