Introduction

Scientific and technological talents participating in transnational academic mobility are essential for knowledge innovation and technology transfer (Chen, 2017). For developing countries, returnee faculty serve as bridges for academic exchanges and scientific research collaboration with developed countries, while also providing home countries with economic, human, and social capital that cannot be obtained solely through local scientific and technological innovation and resource integration (Melin, 2004). Consequently, developing countries like China introduced various talent programs to encourage the return of talented faculty. Simultaneously, Chinese universities are actively recruiting returnees in science and technology to build world-class universities and enhance global competitiveness by creating talent clusters.

Transnational academic mobility enables individuals to expand their social capital and academic networks (Rosen & Zweig, 2003). When scholars return, their previous academic ties with the international community can be relocated to domestic academia (Li & Tang, 2019). As China is a relationship-oriented society, returnees’ previous domestic networks might also affect their professional development. From this context, this study explores the following research question: how do the overseas and domestic academic networks impact returnee scholars’ professional development satisfaction?

This paper is organized as follows: first, we review the literature on strong and weak ties and propose the research hypotheses. The second part introduces the methodology. In the third part, we present the findings of returnee faculty’s dual academic networks and their impact on professional development satisfaction, based on quantitative and qualitative data. Our analysis suggests that maintaining different strengths of ties with members in dual academic networks exerts various impacts on returnees’ professional development satisfaction.

Literature, conceptual framework, and hypotheses

Conceptual framework: strong and weak ties

Ties, or guanxi used in Chinese culture, refer to a connection between two individuals that is subjectively close and potentially resourceful (Bian, 2019). It has been widely demonstrated that the trust, resources, information, and support embedded within these ties have a significant impact on employment, mobility, and career advancement in the labor market. Strong and weak ties are essential branches of tie theory. When synthesizing strong and weak ties, two core aspects can be extracted: the criteria for defining tie strength and the utility of strong and weak ties.

First, regarding the criteria of tie strength, Granovetter (1973) considers it a combination of four dimensions: frequency of interaction, degree of intimacy, degree of emotional attachment, and extensity of resource exchanges. Since the four dimensions are empirically interrelated, they can be characterized using one of the single dimensions (Bian, 2019). Bian (2019) agrees with Granovetter’s criterion, while his definition of tie strength focuses more on the role type: kin ties (parents, spouses, etc.), pseudo-kin ties (teachers-students, masters-apprentices, etc.), and other non-kin ties are the types with decreasing intimacy and tie strength. His view implies a critical idea: an inherent affinity gap between roles leads to differences in mutual responsibilities and obligations. Although this view is empirical in most cases, it fails to cover particular situations (e.g., father-son conflict). Integrating Granovetter and Bian’s views, this study argues that the dynamic frequency of interactions should characterize the operationalized definition of ties strength. Meanwhile, since the intensity and closeness of ties between roles differ, it is necessary to distinguish role types in the ties network when discussing the criteria for classifying tie strength.

The second core dimension involves the utility of strong and weak ties. Granovetter (1973) believes that weak ties have an advantage over strong ties in the labor market. In a network of strong ties, actors and information have a high degree of similarity. Accordingly, information disseminated through strong ties is more likely to be confined to a smaller range, fostering local cohesion while tending to lead to overall isolation and fragmentation (Li, 2003). Weak ties mainly serve as a bridge between two different groups, thus allowing actors to obtain novel information. In contrast, Bian (1997) argues that strong ties are often more effective than weak ties. Favor exchange is usually informal, to some extent, as a violation of formal organizational principles; it must be based on mutual trust, familiarity, and intimacy (Sun & Bian, 2012), while weak ties indicate less trust and a lack of obligation (Bian, 1997).

In general, both strong and weak ties have their strengths. Weak ties have advantages in transmitting heterogeneous information, but they fail to build bridges due to alienation. Strong ties excel at accessing informal opportunities because they imply commitment, trust, and obligation; however, since strong ties are confined to the in-group, the scope of resources involved is narrow, and there is often a high degree of homogeneity.

The strong and weak ties, roles types, and returnee scholars’ professional development

Ties have become an integral part of formal organizations and bureaucratic systems. The use of informal ties to access resources or information is not unique to China (Ji, 2012), and academic fields are no exception. In conjunction with the theme of professional development satisfaction among returnees’ faculty, it is necessary to distinguish different roles within academic networks and investigate the influence of strong and weak ties on professional development satisfaction.

Supervisors, fellow students with the same supervisors, and classmates/colleagues are the most common role types in academic networks, and the intimacy of these roles varies. Supervisors and fellow students with the same supervisors are often classified as shimen at Chinese universities (Liu, 2021), which translates to the same “research family” (Zheng et al., 2018).

Within the shimen, the functions of supervisors and fellow students are different regarding qualifications, knowledge, and resources (Wen, 2022, May 31). In the traditional Chinese culture, supervisor-subordinate forms father-son or mother-daughter relations (Gu et al., 2018), a typical pseudo-kin ties (Bian, 2019). Similarly, the German term Doktorvater (doctoral father) or Doktormutter (doctoral mother) shows an intellectual bond of family intimacy between supervisors and Ph.D. candidates (Holmes et al., 2019). Accordingly, supervisors are not only willing but also capable of offering students enlightening, critical, and future-oriented suggestions and valuable resources. Therefore, we hypothesize (Table 1):

  • H1: More frequent contact with domestic supervisors increases the returnee faculty’s professional development satisfaction.

  • H2: More frequent contact with overseas supervisors increases the returnee faculty’s professional development satisfaction.

Table 1 A summary of hypothesis 1–6
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Frequently, fellow students with the same supervisors do not differ significantly in knowledge, abilities, and the extent and level of their academic networks. During the professional socialization process of graduate training, the concept of shimen is utilized to create a group of individuals with similar research habits, preferences, and ways of thinking (Lin & Chao, 2019; Yao & Yu, 2019). Moreover, they form a well-defined circle; homogeneity is a prerequisite for the group’s existence, and closeness, conservatism, and exclusivity are essential characteristics (Wen, 2022, May 31). However, excessive intra-group consistency and cohesion can lead to groupthink dilemmas, which in turn may result in rigid thinking, limited information flow, unquestioning obedience, stereotypes toward outsiders, and an increased risk of having a narrow vision (Janis, 1991). Based on this, the study posits the following hypothesis:

  • H3: More frequent contact with domestic fellow students with the same supervisors (shimen) decreases the returnee faculty’s professional development satisfaction.

Unlike in China, academic culture overseas seldom has an equivalent concept of shimen (Wen, 2022, May 31). Although there are inevitably similarities in research ideas and directions from the same supervisors, transnational networks are more open and more heterogeneous (Lu, 2014), which can “dilute” and neutralize the negative effects of the closed and redundant nature of the strong shimen ties. Accordingly, heterogeneous transnational networks provide more effective diversified resources to promote academic development. Therefore, we hypothesize:

  • H4: More frequent contact with overseas fellow students with the same supervisors increases the returnee faculty’s professional development satisfaction.

The ties that develop with roles such as classmates/colleagues are often looser than those of members in shimen (Huang, 2021). These ties tend to cross group boundaries, thus facilitating access to heterogeneous resources and information. However, as Qiu and Qiao (2018) argue, the “capability” to help and “willingness” to help are entirely different. When returnees fail to establish stable academic ties with classmates/colleagues at home and abroad, there is no reciprocal channel for exchanging resources and information, and these individuals may not take the initiative to share the resources and information. Maintaining close ties with domestic classmates/colleagues may reactivate local academic networks weakened by lack of communication in overseas study and gain recognition and acceptance (Levin et al., 2011). Based on this, we hypothesize:

  • H5: More frequent contact with domestic classmates/colleagues increases the returnee faculty’s professional development satisfaction.

  • H6: More frequent contact with overseas classmates/colleagues increases the returnee faculty’s professional development satisfaction.

Academic inbreeding and returnee scholars’ professional development

Another concept closely related to the strength of ties is academic inbreeding. It describes the phenomenon of returnees returning to their alma mater, becoming the most significant indicator of domestic academic networks (Li & Tang, 2019). Larger network sizes often translate into greater diversity, providing access to a wide range of resources, opportunities, and non-redundant information (Ynalvez & Shrum, 2011). In contrast, academic inbreeding refers to reproduction within the same category, implying strong ties and homogeneity. Additionally, the exchange of favors, facilitated by trust and support, often requires alum faculty to assume corresponding responsibilities and obligations as compensation, a concept referred to as “rob Peter to pay Paul” (McGee, 1960). Waggoner (1966) bluntly states that “inbreeding is not always bad, but it is dangerous” (p.211). Therefore, we hypothesize:

  • H7: The alumni-faculty status has a negative impact on returnee faculty’s professional development satisfaction.

Methodology

Sample

In this paper, we define “returnee faculty” as those full-time faculty at Chinese universities who either achieved their doctoral degree abroad or have at least two consecutive years of postdoctoral research or work experience at universities or institutions abroad.

This study employs a convergent parallel mixed-method design (Creswell, 2002) to probe the research question. In the quantitative research, we first browsed the homepages of China’s 42 “Double First-Class” universities and sent survey invitations to returnee faculty whose e-mail addresses were available. After three rounds of distribution, 1369 questionnaires were collected, with a response rate of 12.6%. After cleaning the data, a sample of 1307 returnee faculty was obtained. In the qualitative research, we adopted a purposive sampling strategy to identify participants according to their alumni faculty identities and frequency of contact with members in their previous academic networks. Eventually, 13 returnees from nine universities participated in the study, with four participants being alumni faculty (Table 2). Participants’ anonymity and confidentiality were guaranteed to protect the interviewees’ privacy.

Table 2 Demographic information of interviewees
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Data collection

The quantitative data was based on a self-compiled questionnaire with 61 items, exploring overseas learning and research experience abroad, working experience at Chinese universities, and demographic information. The current study focuses on those question items concerning professional development satisfaction and domestic and overseas academic networks. According to the definition of job satisfaction (Locke, 1969; Spector, 1997), we understand professional development satisfaction as employees feel about their overall and systematic development, regarding the fulfillment, and overall positive experience an individual derives from their professional growth (Singh & Singh, 2021). Most research has adopted surveys or bibliometric methods to explore returnees’ research productivity, while few have studied it from an individual perspective. As the self-evaluation approach provides information that other standardized measures cannot obtain (Ross, 2006), we use the self-report method to understand how satisfied returnee faculty are with their professional development. The qualitative data was obtained through semi-structured interviews. The interview questions covered three topics: how returnees received their academic positions, their professional development experience, and their opinions regarding their academic networks.

Data analysis

Quantitative research

Regarding the dependent variable, based on the literature review and pre-interviews, we divide the self-evaluation of professional development into five dimensions: competitive research funding, publications, research collaboration, the extension of original research areas, and the exploration of new research interests. The dependent variables are the above five subscale items and the results of their factor analysis. The five items are chosen for the following reasons: first, tenure track evaluation is mainly based on the quality and quantity of competitive projects and publications. Research collaboration is crucial in promoting projects and publications, and this is particularly true for those faculty with international mobility experience (Wang et al., 2019). We further investigated how returnee scholars explored new research directions and expanded existing research fields to better understand how they perceive their research performance in terms of both breadth and depth (Li et al., 2018). Regarding the independent variable “contact,” participants are required to indicate how frequently they communicate with members of their academic networks.

This study adopts Ordinary Least Squares (OLS) and Propensity Score Matching (PSM) models. The first group of OLS models aims to explore the influence of overseas and domestic academic networks on returnee scholars’ professional development satisfaction. Contact frequency is selected as an operational index to measure the strength of ties (Granovetter, 1973).

The second model explores alumni status’s influence on returnee faculty’s professional development satisfaction. Since the choice of returnee faculty to return to their alma mater is not randomly distributed, it may be influenced by individual and university-level factors, resulting in a self-selection bias. The PSM in a quasi-experimental method is a common approach to tackling the above problems. The core independent variable of this model is whether the returnee is an alum faculty or not. Regarding selecting covariates, “it is important to include in the matching procedure all variables known to be related to both treatment assignment and the outcome” (Stuart, 2010, p.5). Therefore, the covariates selected as matching variables of this study are the variables that affect whether returnee faculty return to their alma mater and their professional development satisfaction. These variables and their detailed descriptions are listed in the control/covariate variable in Table 3. We use the “psestimate” command to filter out the matching variables to achieve the best matching effect. The matching variables finally screened out are shown in Table 7 in the “Appendix” section.

Table 3 Descriptions of variables and descriptive statistics
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Qualitative research

The interview data was probed by thematic analysis, one of the most widely used methods to identify and analyze qualitative data (Braun & Clarke, 2006). The original material was coded word for word, and the passages of text that were identified by the same code were clustered together; we then formed an initial list of codes (e.g., provision of job-position information, research collaboration, willingness to return and work at alma mater); then, we focused on the broader level of themes (e.g., access to academic positions and domestic academic networks) and sorted the different codes into potential themes (e.g., “provision of job-position information” was a subcategory under “access to academic positions”). After that, all codes were refined under more general headings related to the research questions, and a coding frame was formed.

Findings

Dual academic networks and professional development satisfaction

Findings indicate that both overseas and domestic networks are essential for the satisfaction of returnee faculty professional development. The results of inferential statistics suggest that maintaining the appropriate strength of ties with different members of the academic network is critical for returnees (Table 4).

Table 4 Regression results of the influence of academic networks on the professional development satisfaction of returnee faculty
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Frequent contact with domestic and overseas supervisors improves returnee faculty’s professional development satisfaction, supporting hypotheses 1 and 2. Among them, the positive role of the overseas supervisor is omnidirectional. For each unit where returnees are more closely connected with their overseas supervisors, their self-evaluation of professional development in five dimensions, including competitive research funding, publications, research collaboration, the extension of original research areas, the exploration of new research interests, and overall professional development satisfaction, increases by 0.133, 0.141, 0.212, 0.160, 0.141, and 0.187 units, respectively. Besides insufficient promotion role in exploring new research interests, contact with domestic supervisors also shows significant positive effects in other dimensions. The interviewees confirmed the role of supervisors from different perspectives. First, overseas supervisors continue to provide advice for research. For example, Sara mentioned the career advice offered by her former supervisor in the UK:

I rely on my former supervisor’s suggestions in planning my future research focus. He is more familiar with my research and can offer more helpful advice. (Sara)

Similarly, Betty and Alice believed that their overseas supervisors’ guidance facilitated their professional development regarding publication in international journals.

Second, because of the exclusiveness of closed-structured guanxi networks, scarce resources are often only available to the group members. Therefore, maintaining frequent contact with domestic supervisors allows access to scarce academic resources. Jessica mentioned:

Since my supervisor has continuously researched immunization, some specific methods to make good animal models are only available to the members under his supervision. (Jessica)

Findings show that more frequent contact with fellow students in the shimen has a negative effect on all aspects of the returnees’ satisfaction with research advancement; at the same time, contacting students with the same supervisors overseas has a positive impact on the extension of original research areas and overall professional development satisfaction, which confirms hypotheses 3 and 4.

Table 4 also shows that a higher frequency of contact with domestic classmates/colleagues positively impacts returnee faculty’s professional development in all dimensions, and hypothesis 5 is supported. In contrast, a higher frequency of contact with classmates/colleagues overseas does not promise a significant increase in professional development, which rejects hypothesis 6. Interviewees provided some evidence that supports the results. They believed that ties with classmates/colleagues overseas were not close enough to support them to ask the latter for advice when they returned home; moreover, research collaboration across countries was not permissible in terms of time and energy (Emma). At the same time, with the shift in the research field, teaming up with domestic colleagues under the guidance of Chinese government policy is more efficient in researching China-specific issues (Alice).

The alumni faculty status and professional development satisfaction

Before using PSM to estimate the treatment effect, it is advisable to perform balance and standard support checks to test the matching effect. Table 7 in the “Appendix” section shows that the mean difference of each covariate between the treatment group and the control group is no longer significant after matching, and the standard deviation is controlled within 9%. This indicates that the differences in covariates between the two groups are eliminated after matching, and the conditional independent assumption was satisfied. Figure 1 is the test of the standard support hypothesis. It shows significant proximity and coverage between the two groups after matching. The above results show that the matching effect of this study is good, and reliable estimation results can be obtained.

Fig. 1
figure 1

Nuclear density map before and after matching (taking overall professional development satisfaction as an example)

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Since the treatment effect of returnee faculty returning to their alma mater on professional development satisfaction may be affected by the matching method adopted, this study uses radius and kernel matching methods to test the consistency while conducting one-to-one neighbor matching. Table 5 presents the alumni faculty status’s treatment effect on returnees’ professional development satisfaction under various matching methods. Table 5 indicates that after controlling self-selection, alumni faculty status significantly negatively impacts the professional development satisfaction of returnee faculty, and hypothesis 7 is supported. Taking the nearest neighbor matching (NNM) method (k = 1) as an example, in the overall professional development satisfaction, the regression coefficient of average treatment effect (ATT) is −0.139, indicating that alumni faculty’s overall professional development satisfaction is 0.139 units lower than that of non-alumni faculty. The result remains robust under different matching methods. The same is true for the other five sub-dimensions of professional development satisfaction. It should be noted that regarding research collaboration and exploration of new research interests, the coefficient of ATT under the NNM is not significant; however, it is significant in radius matching and nuclear matching.

Table 5 Estimation results of average treatment effect in the treatment group and the control group
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The qualitative data also supports the above research findings. First, having alum status is not always conducive for individuals to expand their academic networks. Scott did not choose to return to his alma mater, and he held that academic mobility facilitated developing a “circle” and occupying a position of structural hole:

(Now) I know my alma mater and the new institution well. I can act as a “glue,” and through me, scholars on both sides can get to know each other. (Scott)

Scott further noted another critical fact that returning to a familiar team leads to narrow-minded thinking, while the non-alumni faculty status provides returnees with more non-redundant information. Similarly, Jessica reiterated that it was often challenging to conduct academic exchanges and discussions equally with former supervisors as alum faculty. Under the “umbrella” of her former domestic supervisor, she usually handles research work with a “Ph.D. candidate” identity and mentality. It was difficult for her to design a research project or establish new academic networks as an independent scholar.

Edward, an alum faculty, also shared his experience. He enjoys the benefits of his alumni status, allowing him to access research resources unavailable to others easily. However, in return for this trust and favor, Edward is required to fulfill his additional obligations. For example, when other colleagues refuse the dean’s request to teach classes in English, Edward is expected to take on the job. In other words, returnees with alumni-faculty status often undertake extra obligations at the cost of the time and energy faculty members have planned to invest in research. In addition, Thomas mentioned that classmates/colleagues often underestimate alum faculties’ academic achievement, as they attribute any academic achievement attained by the returnees to their alum faculty status.

Discussion

This study highlights that maintaining strong and weak ties with role types in dual academic networks impacts returnees’ professional development satisfaction. Findings show that the key to promoting returnees’ professional development satisfaction lies in how returnees adjust the ties’ strength to various roles in the dual academic networks to give full play to the advantages of the strong–weak relations to jointly meet the diverse nature of the individual’s needs (Li, 2007).

First, findings show that keeping strong ties with overseas (I) and domestic supervisors (II) impacts returnees’ higher professional development satisfaction positively (Table 6). Supervisors possess professional knowledge, relatively high social status, and show concern for the personal well-being of the student (Stephens, 2014). The higher the social status of an intermediary, the more beneficial it is for promoting the exchange of social resources and the functioning of resource credit (Sun & Bian, 2017). The trust and reciprocity built through strong ties with supervisors enable returnees to mobilize resources within academic networks and enhance the level of their academic networks and human capital (Baruffaldi et al., 2016).

Table 6 The suggested effective strength of ties with various roles in dual academic networks
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Maintaining strong ties with domestic fellow students doesn’t promote returnees’ satisfaction with professional development (IV), while strong ties with overseas fellow students do (III). One possible explanation is that domestic fellow students and returnees belonging to a relatively closed academic network and members share similarities in research ideas, paradigms, etc. (Lin & Chao, 2019). According to Bourdieu’s theory of habitus, the likelihood “for someone to ‘undo’ their early education” (Swartz, 1997, p.16) is rare. Accordingly, scholars’ deeply-rooted thinking and mindset formed by the former research training will not be easily changed when they are replaced with new research institutions. Such strong ties might lead to similar research ideas and overlapping resources and fall into the dilemma of groupthink (Janis, 1991). The closure of the strong ties decreases the possibilities of extending communication with members in heterogeneous networks, which hinders the formation of interdisciplinary and cross-team communication, highlighting the shortcomings of strong ties. In contrast, though returnees and fellow students in the overseas academic networks also received supervision from the same supervisors, the different research platforms (domestic vs. overseas) neutralized the adverse effects of closure and homogeneity of the strong ties. When scholars return, frequent contact with overseas fellow students will build bridges for information and resource exchange, heterogeneous resources from the international academic community, which may become a meaningful way to achieve high-quality publications (Lu & McInerney, 2016).

One might wonder why the supervisors and fellow students in the shimen are categorized into the strong ties type (Huang, 2021) but have contradictory impacts on returnees’ professional development. Supervisors amass extensive knowledge and academic network connections, and keeping strong ties with them usually results in top-down guidance and one-dimensional resource allocation (Sun & Bian, 2017). However, fellow students in the domestic shimen do not possess the same advantages as supervisors mentioned above. On the contrary, the overlapping resources and redundant information among fellow students have been found to have a negative effect.

Domestic classmates/colleagues (VI) belong to the academic network beyond the shimen boundaries. Fostering closer ties with members in such heterogenous networks empowers returnees to break marginal status, expand the network scale, and expedite integration into the domestic academic community. The results partially confirm Lu’s (2014) view that the more collaborators and stronger ties established with colleagues, the more beneficial to professional development satisfaction. In contrast, ties with overseas classmates/colleagues (V) are inherently loose. Considering the relatively high cost of cross-national communication and the previous status of the weak relations with classmates/colleagues overseas, the time and effort spent contacting them might outweigh their impact on promoting returnees’ professional development satisfaction.

Second, this study explores the impact of alumni-faculty identities, a unique tie within the domestic networks, and results indicate that such status won’t guarantee returnees’ professional development satisfaction. To show loyalty and reciprocity to the home institution, alumni faculty often feel obligated to shoulder more tasks than non-alumni faculty. This finding aligns with Bian’s (1997) concept that trust and obligation are crucial to guanxi networks. In addition, alumni returnees joining research teams led by their former supervisors or senior colleagues might confine their research vision due to the lack of novel information or cross-team interactions, making it challenging to conduct research activities as independent scholars. In contrast, non-alumni returnees can freely explore new research fields. Thus, individuals at the nodes of a structural hole obtain more information, opportunities, and resources and have greater control over the flow of social capital than other individuals (Burt, 1992).

Conclusion

This study examines how dual academic networks influence returnees’ professional development satisfaction. The results show the frequency of contacting various members of the dual academic networks has different impacts on returnee scholars’ professional development satisfaction.

Our findings provide some practical implications. First, previous research explores the effect of ties on individuals’ occupational attainment; this study further applies the impact of the strength of ties and role types on individuals’ professional development satisfaction, both with the overseas and domestic academic networks. The previous study shows returnees’ scientific productivity and research performance are increased when they are embedded in transnational professional networks in their home country or when they are enabled to retain professional linkages with their co-workers and supervisors in the former host country (Jonkers & Tijssen, 2008). This study illustrates that maintaining strong ties with members of the academic network is not always beneficial. Although guanxi is “dyadic in its basic form” (Barbalet, 2021, p.14), it is a continuum system; thus, there are no purely strong or purely weak ties (see Table 6). The relationship between two individuals is not static (Bian, 2019); guanxi building is dynamic (Chen et al., 2013). When time and energy are limited, returnees need to develop a strategy to maximize the strength of both strong and weak ties, while minimizing their weakness, to achieve career development. Second, to increase the overall satisfaction of professional development, returnee scholars need to consider applying for job positions offered by universities that fit their research interests and orientation rather than merely returning to their alma mater for an academic job position.

This research may have the following contributions. First, it is the first time that such a large-scale survey questionnaire has been conducted to cover returnee faculty members from all “Double First-Class” universities in China. Second, we differentiate between the impacts of various roles in returnees’ dual academic networks. This distinction provides valuable insights for guiding returnees in adjusting their strategies when interacting with different members of the academic networks.

This study does have certain limitations. Due to word limits, there has been limited discussion on the in-depth influence of strong and weak ties established with different roles in the academic network on the five dimensions of professional development satisfaction among returnees. Additionally, since this study regarded the frequency of interactions with different groups as a sign of the strength of ties of the academic networks, formal interactions were not clearly distinguished from informal ones, though they are slight differences in concept (Woolley et al., 2008). Finally, this paper only analyzes the overseas and domestic networks jointly by using separate independent variables. A more complex design of independent variables, such as the interaction variables between dual academic networks, will explain more details of the study.