How Does Dialect Ability Affect Migrant Children’s Mental Health in China?—Evidence From The China Education Panel Survey

Background: Mental health is a prominent problem faced by migrant children in China and has a profound impact on their academic and social development. Different from previous studies that emphasize the positive and negative effects of the external system, this paper, considering internal aspects of the migrant children themselves, regards language as an important capital and skill and empirically examines the relationship between dialect ability acquired by migrant children in the area of immigration and their mental health. Methods: Data are from the China Education Panel Survey of 2015. One-way ANOVA and multiple linear regression are used to investigate the inuence of dialect ability on migrant children's mental health. Mediating effect analysis is used to examine the role of school integration between dialect ability and migrant children’s mental health. Results: Dialect ability is an effective protective factor for migrant children’s mental health. The more procient they are in local dialects, the higher their mental health level. School is the center of the interaction between migrant children and the place of immigration and the main space in which they use the local dialect. Mediating effect analysis shows that, in this eld, migrant children with good dialect ability can achieve social integration by expanding their school communication, enhancing their school identity and winning peer acceptance to maintain and improve their mental health. Conclusions: This shows that migrant children’s mastery of local dialects is conducive to their psychological development, and school integration acts as an important bridge between local dialect and migrant children's mental health, which reveals the importance of advocating language diversity and cultural integration.

the negative evaluation of migrant children's mental health has persisted over time [16,17]. This not only concerns the academic and social development of the migrant children themselves but also affects the stability and development of their families and even the whole society; thus, this issue has become a focus of academic research.
It is crucial to address the mental health problems of migrant children, and this is the core topic of the research on migrant children's mental health [18]. Scholars have found that in general, the various factors affecting migrant children's mental health can be summarized into three levels: the macro-level social environment, the meso-level characteristics of school and the community, and the micro-level family background [19]. Regarding the macro social environment, the long-existing dual system of urban-rural division, household registration system and the implied cultural differences between urban and rural areas not only make migrant children frequently suffer social exclusion but also easily lead to identity crisis and pressure [20,21]. In terms of school and community characteristics at the meso level, differentiated arrangements (such as special schools for migrant children or designated public schools), unfair treatment by teachers and discrimination by classmates constitute a special aspect of migrant children's learning, while geographical remoteness, poor conditions and noisy environment are common phenomena in this group's living spaces [19,22]. For the micro family background, low socioeconomic status, poor parenting style and poor interpersonal relationships make it di cult for migrant children's families to act as a protective net against their mental health risks [23]. Moreover, these different levels of in uencing factors interweave with each other, further aggravating the psychological plight of migrant children [19].
The mental health of migrant children, who act as agents in social situations, should be the product of the interaction between individuals and the environment [24]. In addition to the external in uence from various ecosystems in immigrant areas (such as the family, school, community and society), the internal aspects of migrant children should not be ignored [25]. In past studies, more attention has been given to personality factors, such as self-e cacy, resilience and personality tendency [26][27][28]. However, the capital and skill factors of migrant children are seldom discussed. Among them, language ability is rarely considered in the mental health research of migrant children in China. Language can be decoded into symbols (such as voice or words) by people for communication. In terms of linguistics, language is a basic medium of communication that shows its value in communicative function and enables people to exchange information and express emotions. Since World War II, linguistic economics has enriched the practical value of language. Language is regarded as a form of human capital with economic characteristics, such as utility, costs and bene ts [29]. In the 1960s, with the addition of sociology and sociolinguistics, the explicit function of language was further expanded. Language became a signal of social identity, depicting identity selection, comparison and belonging. Currently, language has many functions in communication, economy, society and culture [30]. It has a wide range of value attributes and has a profound impact on all aspects of people's lives.
The in uence of language ability on migrant children's mental health should not be underestimated. In recent years, with the rise of cultural sociology, language has been developing into a key analytical variable, and many immigration-related language studies show that language plays an important role in people's psychology and practice and include it in the interpretation of social consequences variables (such as income, behavior, psychology) [31]. These studies show that the language pro ciency or bilingual ability of migrants can effectively improve their self-rated health and mental health. Schachter et al. show that bilingual migrants who are pro cient in their mother tongue and the local language (such as English) can better self-assess their physical and mental health because they can obtain more economic status or social support [32]. Wong also proves this from the opposite side, and he nds that limited English pro ciency has negative effects on the mental health of Chinese people living in the United States. The language barrier leads to poor social life adaptation, underutilization of mental health services or premature termination of treatment, which signi cantly reduces the mental health level of Chinese residents compared with native American residents with good English pro ciency [33].
Dialect, also known as "Tuhua", is a local variant of language, which is different from the standard language (such as Mandarin Chinese) and is used only in a certain area. China has a vast territory and diverse cultures, and each region has its own dialect. Relevant statistics showed that, there were 10 dominant dialects in China (Mandarin, Cantonese, Wu, Jin, Min, Hui, Gan, Xiang, Pinghua, and Hakka), including 114 subdialects, and different dialects even exist between counties (districts) in the same province [34]. Although the government began to promote Mandarin Chinese in the mid-1950 s, dialects have not withdrawn from the stage and are still widely used in people's daily lives.
Living across counties (districts) is the most signi cant identity of migrant children, distinguishing them from other children. Although the entire family may move together from the hometown to the area of immigration, the external environment of the family changes greatly, which leads to the loss of rights and interests in some aspects. Children need to readapt to the unfamiliar environment, and in this process, their mental health is affected to a certain extent [35]. On the one hand, an unfamiliar language is an important factor of the macro-level external environment for migrant children [36]. The types and uses of dialects in China are extensive, and there are great differences across regions. Migrant children shuttling across different counties (districts) often face dialect problems that are no less severe than the language distance international immigrants face in a certain sense. Their adaptation and mastery of the dialects in the area of immigration are related to their mental health. On the other hand, because most migrant children are of school age and receive compulsory education in the new area, the unfamiliar school environment is an important meso-level external environment for them and a key place for their socialization [37]. The social integration of migrant children in schools is directly related to their psychological development. Those with better social integration will maintain positive states, such as happiness, pride and satisfaction, while those with insu cient social integration often face negative emotions, such as anxiety, loneliness and inferiority complex. Moreover, for migrant children, dialect and school environment are two unfamiliar environments which are interrelated. Dialect, as the carrier of local culture, is regarded as the main means for migrant children to achieve social or school integration [36]. It can not only shorten the distance between different ethnic groups and reduce discrimination and exclusion but also increase communication and mutual assistance between different ethnic groups and enhance identity and belonging [38]. Therefore, this paper considers migrant children themselves from the language perspective and uses the most recent nationally representative data (CEPS2015) to analyze the relationship between school-age migrant children's local dialect ability and their mental health. Furthermore, it examines the mediating effect of school integration in this relationship to provide new ideas for promoting the mental health development of children in this group. Through this study, we found that migrant children with good dialect ability tend to have higher mental health levels. In addition, School is the center of the interaction between migrant children and the place of immigration and the main space in which they use the local dialect. School integration has not only signi cant positive effects on migrant children's mental health, but also acts as an important bridge between dialect ability and migrant children's mental health.

Data and Sample
This paper uses data from the China Education Panel Survey (CEPS) designed and completed by the National Survey Research Center at Renmin University of China in 2015. The survey is a nationally representative survey that tracks comprehensive aspects of education. All seventh grade students in the 2013-2014 academic year baseline survey were followed up. A total of 9450 students were successfully followed up, 830 were lost to follow up, and 471 were newly enrolled. There were 10751 samples. The survey objects include students, parents, teachers and school leaders. The survey content involves students' basic information, school performance, physical and mental health, social development, family education, class environment, school characteristics and many other contents, which can well meet the needs of this study.
According to the analysis object requirements of this study, we screened 1769 migrant children through the "registered address (i.e., whether it is in the county or district)" and the speci c registered permanent residence of the students interviewed. After deleting a small number of invalid values and missing items, the nal effective sample included in the analysis was 1279.

Dependent Variable
The dependent variable is mental health. It focuses on the recent social psychological state of the students surveyed and uses a set of indicators constructed by six questions in the CEPS for measurement. The question set is as follows: "In the past seven days, have you had the following feelings: 'Depressed', 'Downhearted', 'Unhappy', 'Slouching', 'Sad', 'Nervous'." The answer options for each question are "Never", "Rarely", "Sometimes", "Often" and "Always". We adjust the score of each question in reverse and record 5-1 points. In addition, to simplify the data analysis, principal component analysis is used to extract common factors and convert them into a mental health index with a value range of 1-100 points. The higher the score is, the higher the mental health level of the migrant children.

Independent Variable
The independent variable is dialect ability. Many scholars use self-reported language pro ciency to measure migrants' ability to master the local language [39]. Therefore, this variable is mainly measured by the students' mastery of the local dialect. The CEPS includes the question "Do you know the local dialect?" The answer options are divided into ve grades: "Totally not", "Understand only", "Speak only a little", "Basically speak but not pro ciently" and "Speak uently". We record the answers from 1-5 points, where the higher the score is, the stronger the dialect pro ciency of the migrant children.

Mediator Variables
The mediator variable is school integration. According to the two-way interaction theory of integration developed by scholars in China and internationally, school integration should be regarded as the changing process and state of the interaction between migrant children and the society in the destination [37]. It is neither the one-way and passive integration of migrant children nor the simple rejection or acceptance of the society in the destination. Considering the particularity of the school-age years regarding identity, learning and life, school integration can be considered in three dimensions: school interaction and identi cation, representing students' self-integration, and peer acceptance, re ecting others' recognition of students at school. The speci c explanation is as follows.
The dimension of school communication is measured by migrant children's network of friends in school. The CEPS includes the following question "Please list the names of your ve best friends (if there are not ve, ll in a few). Do they share the same school with you?" The answer options to this question are "Yes" and "No", which are recorded as 1-0 points. After summing up, a continuous variable with a value range of 0-5 points is obtained. The higher the score is, the wider the school communication of migrant children.
The dimension of school identity is measured by migrant children's emotional belongingness and identity with the school. It is composed of four scales in the CEPS: "I often participate in activities organized by school or class", "I feel close to people in this school" and "I hope to go to another school (reverse scoring)". After summing up, a continuous variable with a value range of 3-12 points is obtained. The higher the score is, the stronger the school identity of migrant children.
The dimension of peer acceptance is measured by the acceptance, recognition and friendliness of the students in the county (district) school towards migrant children. There are three questions in the CEPS: "Do your classmates registered in this county (district) want to be friends with those from other cities?", "Do your classmates registered in this county (district) want to be friends with those from other rural areas?" and "Most classmates are friendly to me." 1-0 points are recorded for the options "willing (agree)" and "unwilling (disagree)", respectively. After summing up, a continuous variable with a value range of 0-3 points is obtained. The higher the score is, the better the acceptance of peers in the school.

Control variables
The control variables involve individual, family and school characteristics. The individual characteristics of students include household registration type, whether the child is an only child or not, whether the child is often ill or not, self-e cacy and con dence in the future. Family characteristics include family structure, family economy and family relationship. School characteristics include school type, school location and whether health education is offered. Second, a multiple linear regression model is used to investigate the in uence of dialect ability and school integration on migrant children's mental health. Third, a mediating effect analysis is used to examine the role of school integration between dialect ability and migrant children's mental health. Twosided P-values less than 0.05 are considered statistically signi cant.

Results
The In uence of Dialect Ability on Migrant Children's Mental Health Dialect is an important capital and skill of an individual. Its learning and mastery is a process of knowledge accumulation, which requires considerable time and energy. Data from the CEPS2015 show that, overall, the average score of dialect pro ciency of school-age migrant children is 3.38, which is between "speak only a little" and "basically speak but not pro ciently". Speci cally, in this group, when asked "Do you know the local dialect?", 12.20% of them chose the option "Totally not", 20.72% of them chose "Understand only", 15.95% of them chose "Speak only a little", 19.08% of them chose "Basically speak but not pro ciently", and 32.06% of them chose "Speak uently". Therefore, the vast majority of school-age migrant children are more or less aware of the local dialect.
Migrant children span different counties (districts), and they may face challenges in life, learning and physical and mental development in the areas of immigration due to dialect differences. Table 2 reveals the mental health level of migrant children with different dialect abilities. On the whole, the average score of migrant children's mental health was 69.48, which was above the average level. Speci cally, in this group, the average scores of those who chose "Totally not", "Understand only", "Speak only a little", "Basically speak but not pro ciently", and "Speak uently" were 65.29, 69.32, 68.03, 70.53, and 71.29, respectively. It can be seen that the mental health of migrant children is consistent with their pro ciency in local dialects, generally showing an optimistic state of steady increase with uency. This nding preliminarily veri es the promotion effect of dialect ability on mental health. To accurately re ect the impact of dialect ability on migrant children's mental health, we adopt the method of gradually incorporating control variables to estimate the model to obtain a robust regression result. Table 3 shows that the regression coe cient of dialect ability in model 1.1 is 1.192, which passes the test at the signi cance level of 0.01. This shows that the better migrant children's dialect ability is, the higher their mental health level. In model 1.2, the following control variables are added on the basis of model 1, such as student characteristics, family characteristics and school characteristics. Although the regression coe cient of dialect pro ciency decreases, it is still positive (1.140) and passes the test at the signi cance level of 0.01. The ndings con rm the positive correlation between dialect ability and migrant children's mental health.   Table 5 further examines the mediating effect of school integration on dialect ability and migrant children's mental health and speci cally examines the role of three dimensions of school integration. The results show that the total effect coe cient of dialect ability is 1.140, and it passes the statistical test at the signi cance level of 0.01, indicating that dialect ability constitutes an effective protective force for migrant children's mental health, and its effect is 1.140, which is the same as the conclusion of model 1.2. Among them, the direct effect coe cient of dialect ability passes the statistical test at the signi cance level of 0.05, which shows that dialect ability can still positively affect the mental health of migrant children after the mediator variable of school integration is added, and its effect is 0.944, accounting for 82.80% of the total effect. The indirect total effect coe cient of dialect ability passes the statistical test at the signi cance level of 0.01, which shows that school integration has a positive mediating effect between dialect ability and migrant children's mental health, and its effect is 0.196, accounting for 17.20% of the total effect. Among them, the indirect effects of school interaction, school identity and peer acceptance are 0.041, 0.153 and 0.002, accounting for 3.59%, 13.46% and 0.15% of the total effect, respectively.
Then, how can we understand the relationship chain between local dialect ability, school integration and mental health? The most essential function of language is communication, which is not only the expression of language but also the collision of identity. People establish their relationship with society in the process of discourse communication. The social identity of the participants, such as birthplace, has an impact on the use of language. Social identity and language restrict each other; that is, social identity determines the way of language operation, and the way of language operation reacts to the identi cation of others with social identity [40]. Migrant children have certain life experiences and insights into the area of immigration. They care not only about their personal identity but also about their social identity. Therefore, when they communicate with others, they often choose the discourse types corresponding to different situations, relationships and personal factors to enhance their image and obtain recognition. When migrant children enter school in the area of immigration, the language environment is relatively complex. In addition to Mandarin, the local dialect is dominant. Therefore, in their daily study and life, teachers or students are more likely to adopt their familiar and intimate local language for communication. Migrant children's efforts to speak the local dialect not only conveys the friendly signal of actively integrating into the local society (such as local peers) but can also reduce the exclusion and discrimination of the local society, win trust and favor, broaden the children's study and life circle, and strongly support the maintenance or improvement in their mental health level.

Discussion
Increasing attention has been given to the relationship between language ability and the social psychology of children and adults. Many studies have shown that language is an important human ability that supports the functions of individual communication, thinking, self-con dence and identi cation and plays a positive role in the development of people's mental health [41][42][43]. The study of migrant children in China provides a unique opportunity to explore the relationship between language and mental health because the nature of these children's language problems is not based on neurolinguistic disorders or general cognitive de cits. China has a vast territory and a rich cultural heritage. In addition to the o cial language (i.e., Mandarin Chinese) promoted by the government, all localities retain their own unique languages (i.e., dialects), which are quite different from each other [34]. The ndings of this study are consistent with previous studies on the relationship between language and mental health. Language is not only the most important part of culture but also the basic medium for the transmission of culture across time and space, and at the regional level, the cultural characteristics of a region are rst presented by dialect. Therefore, the individual's mastery of the local language directly re ects his ability to adapt to the local cultural environment [44]. According to Berry's cultural adaptation stress model, children with multilanguage ability are actually in "integration" mode; they face less pressure of cultural adaptation and have better social and psychological conditions. In contrast, those facing special language disorders are in "nonintegration" mode and will bear more cultural adaptation pressure and face a greater risk of suffering from various psychological and mental diseases [45]. For example, Conti-Ramsden and Botting demonstrated a markedly higher rate of anxiety, loneliness and depression symptoms in adolescents with speci c language impairment [46].
The ndings of this study extend the research on language ability and mental health. In China, many scholars have discussed the economic impact of language on the oating population. For example, Chen et al. analyzed survey data of the oating population in rural and urban areas of Shanghai and found that the use of the Shanghai dialect had a positive effect on their work and income [31]. Wang Hai-xia et al. analyzed CLDS data and found that mastering appropriate dialects was conducive to improving the income level of the oating population [47]. There is a relative lack of attention to the noneconomic consequences of poor dialect ability, such as mental health. In other countries, although many scholars have investigated the impact of language on immigrants' mental health, the research objects are mainly international immigrants. For example, Ortiz and Arce's research on Mexican Americans found that the single use of either Spanish or English leads to worse psychological status, and people who use two languages equally achieve better cultural integration and mental health [48]. Howey et al. also found that Korean immigrants' excessive use of Korean has a negative impact on their psychological development [49]. This paper focuses on migrant children in China, and there are some differences between Chinese migrant children and children of transnational immigrants in terms of institutional environment, cultural background, migration and mobility mode.
The ndings of this study also promote the analysis of the relationship between language ability and mental health. Although the association between language and mental health has been illuminated by previous studies, the mediating variables in the relationship between language and mental health are not clear [50,51]. Therefore, as Pennebaker et al. indicated, there is a need for a more theorized approach in the explanation of the link between language and psychopathology [52]. Guided by the theory of social integration, our study points out that school is the center of the interaction between migrant children and their place of immigration as well as the main place where they use dialects. Having a strong dialect ability can help migrant children achieve social integration by expanding their school communication, enhancing their school identity, and winning peer acceptance, thus contributing to their mental health development.
Of course, there are some limitations in this study. First, because the analyzed data are from CEPS, we analyze migrant children in the compulsory education stage and lack attention to migrant children in other stages of education, such as senior high school. Second, related to the rst point, the exploration of the relationship between dialect ability and migrant children's mental health focuses on the school space and pays little attention to other external aspects, such as community support. Finally, limited by the data available, this paper focuses on the local dialect of the place of immigration but pays little attention to the in uence of the dialect in the emigration area or the o cial language (Mandarin Chinese). These are future research directions that may be better understood through follow-up investigations.

Conclusions And Policy Implications
With the rapid development of new urbanization, increasing attention has been given to the mental health of migrant children. Studies examining the mental health of migrant children consider internal or external factors. The former refer to aspects of the migrant children themselves, while the latter focus on the social environment. Different from the previous studies that overemphasize the external effects of the ecological system in the area of immigration, this paper, considering the migrant children themselves, analyzes the in uence of dialect ability on mental health from the perspective of language, guided by social integration theory.
In summary, based on the data of the CEPS2015, our study shows that in China, nearly 90% of migrant children have a certain understanding of the local dialect, and more than 30% have mastered the local dialect pro ciently. Different from the economic impact of dialect ability for migrant adults, dialect ability brings noneconomic returns to migrant children; namely, migrant children with good dialect ability tend to have higher mental health levels. Moreover, after controlling for personal characteristics, family characteristics and school characteristics, the mental health effect of dialect ability is still signi cant and has strong stability. In addition, because school is the most important living space for migrant children in the area of immigration, it is also the communication space in which dialect ability affects migrant children's mental health. Our study shows that school integration helps maintain and improve the mental