Large Language Models (LLMs) have emerged as dominant foundational models in modern NLP. However, the understanding of their prediction process and internal mechanisms, such as feed-forward networks and multi-head self-attention, remains largely unexplored. In this study, we probe LLMs from a human behavioral perspective, correlating values from LLMs with eye-tracking measures, which are widely recognized as meaningful indicators of reading patterns. Our findings reveal that LLMs exhibit a prediction pattern distinct from that of RNN-based LMs. Moreover, with the escalation of FFN layers, the capacity for memorization and linguistic knowledge encoding also surges until it peaks, subsequently pivoting to focus on comprehension capacity. The functions of self-attention are distributed across multiple heads. Lastly, we scrutinize the gate mechanisms, finding that they control the flow of information, with some gates promoting, while others eliminating information.