%0 Conference Proceedings %T Language Model Decomposition: Quantifying the Dependency and Correlation of Language Models %A Zhang, Hao %Y Goldberg, Yoav %Y Kozareva, Zornitsa %Y Zhang, Yue %S Proceedings of the 2022 Conference on Empirical Methods in Natural Language Processing %D 2022 %8 December %I Association for Computational Linguistics %C Abu Dhabi, United Arab Emirates %F zhang-2022-language %X Pre-trained language models (LMs), such as BERT (Devlin et al., 2018) and its variants, have led to significant improvements on various NLP tasks in past years. However, a theoretical framework for studying their relationships is still missing. In this paper, we fill this gap by investigating the linear dependency between pre-trained LMs. The linear dependency of LMs is defined analogously to the linear dependency of vectors. We propose Language Model Decomposition (LMD) to represent a LM using a linear combination of other LMs as basis, and derive the closed-form solution. A goodness-of-fit metric for LMD similar to the coefficient of determination is defined and used to measure the linear dependency of a set of LMs. In experiments, we find that BERT and eleven (11) BERT-like LMs are 91% linearly dependent. This observation suggests that current state-of-the-art (SOTA) LMs are highly “correlated”. To further advance SOTA we need more diverse and novel LMs that are less dependent on existing LMs. %R 10.18653/v1/2022.emnlp-main.161 %U https://aclanthology.org/2022.emnlp-main.161 %U https://doi.org/10.18653/v1/2022.emnlp-main.161 %P 2508-2517