Injecting Knowledge into Biomedical Pre-trained Models via Polymorphism and Synonymous Substitution
This addresses the issue of low-frequency knowledge loss in biomedical PLMs, offering an incremental improvement for domain-specific applications.
The paper tackles the problem of relational knowledge being underexpressed in pre-trained language models due to report bias, proposing a method to inject such knowledge by switching entities to related ones, which improves performance in biomedical downstream tasks.
Pre-trained language models (PLMs) were considered to be able to store relational knowledge present in the training data. However, some relational knowledge seems to be discarded unsafely in PLMs due to \textbf{report bias}: low-frequency relational knowledge might be underexpressed compared to high-frequency one in PLMs. This gives us a hint that relational knowledge might not be redundant to the stored knowledge of PLMs, but rather be complementary. To additionally inject relational knowledge into PLMs, we propose a simple-yet-effective approach to inject relational knowledge into PLMs, which is inspired by three observations (namely, polymorphism, synonymous substitution, and association). In particular, we switch entities in the training corpus to related entities (either hypernyms/hyponyms/synonyms, or arbitrarily-related concepts). Experimental results show that the proposed approach could not only better capture relational knowledge, but also improve the performance in various biomedical downstream tasks. Our model is available in \url{https://github.com/StevenZHB/BioPLM_InjectingKnowledge}.