Based on his idea of ??apperception, Herbart divided the teaching process into four stages, namely the four-stage teaching method: 1. Understanding - teaching new knowledge to students clearly; 2. Association - new knowledge To establish connections with old knowledge; 3. System - make generalizations and conclusions; 4. Method - apply the learned knowledge to practice (exercise solutions, written assignments, etc.). The students' psychological states corresponding to these four stages are: attention, expectation, exploration and action.