This paper expounds the basic viewpoints of four early immigration theories.

(1) formal training is based on functional psychology, which holds that all kinds of human activities are dominated by corresponding functions, and all kinds of functions engage in different activities, and migration can only be produced through a "formal training" process. Migration is unconditional and automatic. (2)*** with elements. Migration only happens when there are the same elements or * * * the same elements in two cases. The more the same connections, the greater the migration. Migration is very specific and conditional, and it requires the same elements. (3) Experience categorization theory. Judd's experience categorization theory emphasizes the role of generalized experience or principle in transfer. Judd believes that the key to transfer is that learners summarize the principle of * * * between them in two activities. (4) Relationship transformation theory. Whether the acquired experience can be transferred depends on whether individuals can understand the overall relationship between various elements and the relationship between principles and practical things, that is, understanding and epiphany of all relationships in the situation is the most fundamental factor to obtain general transfer.