Interest is based on need. Need to have spiritual needs and material needs, interest is based on spiritual needs (such as scientific and cultural knowledge, etc.). If people feel the need for something or an activity, they will be eager to contact and observe it, actively engage in this activity, and pay attention to exploring its mystery. Interest is associated with cognition and emotion. If you don't know something or an activity, you won't have feelings for it, so you won't be interested in it. On the contrary, the deeper you know, the more intense your feelings will be and the stronger your interest will be.

People's interests are varied, but in a nutshell, they can be divided into three categories:

First, material interests and spiritual interests. Material benefits mainly refer to people's interest and pursuit of comfortable material life such as food, clothing, housing and transportation; Spiritual interest mainly refers to people's interest and pursuit of learning, research, literature and art, knowledge and other spiritual life. As far as middle school students are concerned, because their outlook on life and world outlook has not yet been fully formed, both material interests and spiritual interests need teachers' active guidance to prevent abnormal development in material interests and negative development and pursuit in spiritual interests.

Second, direct interests and indirect interests. Direct interest refers to interest in the process of activities. For example, some middle school students are imaginative and creative, and like to make various models. In the production process, they are absorbed and show strong interest; Indirect interest mainly refers to the interest in the results produced by the activity process. Some middle school students like painting in their spare time. Whenever they finish a painting, they will show great interest in their achievements. Direct interests and indirect interests are interrelated and mutually reinforcing. Without direct interest, the process of making various models is very boring. Without the support of indirect interests, there will be no goal and the process will be difficult to last. Therefore, only by organically combining direct interest with indirect interest can we give full play to our enthusiasm and creativity, persevere, have clear goals and achieve success.

Third, personal interests and social interests. Personal interest refers to the positive, tendentious and selective attitudes and emotions that individuals have towards specific things, activities and people. Social interest refers to the general interest of social members in a certain field or the general demand for social members in a certain field.