Hu Baotan, a writer in Shanghainese, once told this joke: “Now some middle-aged and elderly people on the road, one hand holding a child, one hand walking a dog, a dog; speak Mandarin with the child, head back over, with the dog but speak Shanghainese.” As a cosmopolitan city, this joke is a true reflection of the popularity of Mandarin in Shanghai. But what is the difference between Shanghainese and Mandarin? From its origin, Shanghai dialect is a Wu language, which has a history of thousands of years, and the modern Wu language is closer to Middle Chinese. Mandarin comes from Manchu official dialect, which is only a few hundred years old. So there are considerable differences in vocabulary, grammar, and pronunciation between Shanghainese and Mandarin. When I first came to Shanghai, I was confused about the Shanghai dialect around me, like listening to a book from heaven. Today, I had a joke when a patient came to our integration clinic and talked about his child’s condition with the doctors around him in Shanghainese, while I was listening to the book from heaven, as if I had traveled to another planet. Today, when the patient came to our clinic and said he had already told me about his condition, I was baffled… Later, everyone laughed and the family said, “You must speak to me in Mandarin in the future! What about adults, what about babies who are just learning to speak in a different language? Look at the following cases! Case 1: Toto is three years old, but he can only call “daddy” and “mommy”, he can say 5~6 words, but he can’t say sentences, and in the last month, he didn’t say any words, and he completely used his fingers and feet instead of his poor speech. The mother was very worried. After the doctor’s examination and questioning, it was found that Duo’s home language environment was complicated. The complex language environment and frequent changes in language pronunciation caused Toto’s intelligence and language to lag behind, and the frequent environmental changes also made Toto’s mind constantly adapt to the changes in the surrounding environment, and the child became sensitive and suspicious and insecure. Case 2: Lele is four years old and can communicate normally with others, but her mother found that Lele’s pronunciation is very unclear and sometimes she even misunderstands what Lele says. After the doctor’s examination and questioning, it was found that Lele’s family language environment is also complicated, her father is from Shanghai and her mother is from abroad. What happened to Dodo and Lele? What is wrong with their language when Shanghainese meets Mandarin? In a complex language environment, children are involved in one language before they are familiar with the expressions of another language, and they have to learn another language before their phonological and grammatical rules are established, which can easily lead to confusion, errors or even delays. For example, the delay of Toto is a sign of delayed speech and language development. The mispronunciation of Lele is a sign of functional dysarthria. Delayed language development refers to children whose verbal ability or language comprehension is significantly behind the normal developmental level of children of the same age due to various reasons. Low intelligence, hearing impairment, and dysarthria may cause delayed language development in children, but one common clinical cause is poor language environment. Functional dysarthria is a condition in which the baby’s phonological organs have no morphological or motor abnormalities, and the hearing and intelligence are at normal levels, but there are slurred speech sounds. This is the case of Lele. In the above two cases, the children are in a complex language environment. Many mothers believe that “the earlier the language skills are developed, the smarter the baby will be” and that they cannot let their babies “lose” at the starting line, but they do not anticipate that they will fall into the misunderstanding of language development, which will instead The development of the baby’s language skills will be affected. Children in a family with more than two dialects are more likely to have developmental language disorders than children in a monolingual environment, especially in children between the ages of 2 and 3. Children in this age group are learning to imitate language, and an overly complex home language environment can confuse children and cause them to speak later than others. Dr. Feng Jincai, deputy chief physician, recommends that until the age of 2, children should be exposed to a single language environment as much as possible. Once they are good at speaking their native language, they can learn a foreign language.