This chapter explores the application of large language models (LLMs) to psycholinguistic testing, focusing on Korean LLMs and the linguistic phenomena in Korean. The widespread impact of LLMs has reached various fields, including linguistics. Through methods such as surprisal analysis and prompt engineering, LLMs have demonstrated that they are viable nonhuman subjects for linguistic experiments. Case studies from morphosyntax to pragmatics illustrate the design and execution of experiments using LLMs. This chapter also discusses the advantages and limitations of LLMs for psycholinguistic testing. Although LLMs offer accessibility and novel research opportunities, concerns about their psychological plausibility persist. The vast parameter size of LLMs must be comparable to human subjects, and the extent to which they genuinely understand natural languages remains under scrutiny. Ultimately, this chapter aims to highlight the potential and challenges of integrating LLMs into psycholinguistic research.