Memory is the reproduction of past experiences and things that have happened in the human brain, including the process of remembering, retaining, recalling and recognizing (reproduction). In this process, things are processed by classification, generalization, comparison, connection, etc. Therefore, recall is the reproduction of past experiences by the human brain after processing, so there are partial or complete distortions or errors. In clinical work, memory can be divided into the following three types according to the length of recall time: ① Immediate memory: refers to the memory of things that can only be maintained for less than 1 minute, which is generally easy to forget. Give the examinee a string of numbers and ask him to recite or recite them backwards. The subject must have normal attention. The capacity of information that can be processed is limited, only about 7 digits. ② Recent memory: Memory of things within a few minutes to a few days. ③ Remote memory: Memory of things from a few months to many years ago.