Extracting Linguistic Information from Large Language Models: Syntactic Relations and Derivational Knowledge

This paper presents a study of the linguistic knowledge and generalization capabilities of Large Language Models (LLMs), focusing on their morphosyntactic competence. We design three diagnostic tasks: (i) labeling syntactic information at the sentence level -identifying subjects, objects, and indirect objects; (ii) derivational decomposition at the word level -identifying morpheme boundaries and labeling the decomposed sequence; and (iii) in-depth study of morphological decomposition in German and Amharic. We evaluate prompting strategies in GPT-4o and LLaMA 3.3-70B to extract different types of linguistic structures for typologically diverse languages. Our results show that GPT-4o consistently outperforms LLaMA in all tasks; however, both models exhibit limitations and show little evidence of abstract morphological rule learning. Importantly, we show strong evidence that the models fail to learn underlying morphological structures. Therefore, raising important doubts about their ability to generalize.