Before Seers (1989) proposed the concept of TMX, although, scholars pay more attention on the organization’s vertical exchange relationship-Leadership-Member Exchange (LMX), although “team” as the basic task execution unit has been widely and popularly used. As Leadership-member exchange theory has shown, employees’ remuneration, and promotion opportunities in large extent depend on their relationship with their leaders, especially when leaders master a large amount of resources in the organization [6] . Therefore, the LMX relationship exerts a significant impact on employee performance, job satisfaction, organizational citizenship behavior, organizational commitment, and turnover intention [7] [8] . However, with the emergence of Shared Leadership [9] and Self-managed teams [10] [11] , impact of leadership may be relatively weakening. In other words, the interaction between team members has a more obvious effect on individual performance and team performance. That’s why understanding the role of horizontal exchange relationship in the work team is particularly urgent and important [12] . In such context, Seers (1989) proposed the concept of TMX basing on role theory and social exchange theory. TMX refers to the reciprocal exchange process between team members, including a member who not only aids, ideas, willingness to respond, to others but also get a certain degree of information, help and recognition from other members [5] .

Once the concept of TMX was proposed, it attracted attention from academic community. The main reason for that can be summarized into two points. Firstly, TMX can promote comprehensive understanding of the internal exchange relationship of the team. To be more specific, in the team, while LMX can only reflect the vertical exchange relationship between leaders and members, TMX as a horizontal exchange relationship variable within the team is able to play a supplement role to the LMX relationship, which can also contribute to understanding of TMX in academic area [13] . Secondly, “team” is highly concerned about in the practical and academic area. With team-based work design increasingly thought highly of, more and more scholars began to figure out influencing factors of team output such as team innovation, team performance, team effectiveness, and team creativity. As for practical area, they hope for get more theoretical as well as practical guidance from academia too.

Seers (1989) proposed the concept of TMX based on role theory and social exchange theory, which means the process of reciprocal exchange between team members, including a member offer help, ideas, feedback for others and the degree of obtaining information, help, and recognition from other members [5] . TMX reflects the individual’s overall perception of the quality of the work relationship within the team [14] . Unlike the leadership-member exchange (LMX) theory, which focuses on the vertical relationship between leaders and members [15] , TMXs reflect the overall, horizontal reciprocal relationship between a member and other colleagues. Therefore, it is more representative of the quality of relationships at the team level [16] . Seers (1989) argues that in a self-management team, team members attitude and engagement towards work are related to such reciprocal relationship between team members [5] . Specifically, the higher the quality of TMX, the stronger the reciprocity between the members will be [12] . That is, if everyone’s pay will be recognized and rewarded by others from team, then they are more willing to make contributions to achieve team goals together. On the contrary, the lower the TMX, the less likely the member’s efforts are to be respected and rewarded by others, and correspondingly less willing to make efforts to abstain team goals. So TMX reflects the spirit of mutual assistance and altruism between team members [17] and the spirit of “rewarding oneself” [18] . Especially in innovative self-management teams (such as R & D teams), single member with limited knowledge as well as capabilities usually fail to finish tasks for uncertainty and complexity of the task itself [19] . Instead, team goals can be effectively realized through collective power can be effectively realized. Thus, the process of interaction, mutual assistance, and information sharing among team members plays a crucial role in the creation of innovation results.

However, only a qualitative study published by Tse and Das borough in 2008 involves types of TMX until now. Based on the definition proposed by Seers (1989), Tse and Dasborough (2008) used qualitative research methods to identify two types of TMXs: task-oriented exchange and relation-oriented exchange [20] . Task-oriented exchanges means for idea sharing, feedback, information, and knowledge sharing, relationship-oriented exchanges include help, care, support, similar values and standards, intimacy of relationship, private sharing, friendship, and encouragement [20] . They further propose that TMX in low Quality contains only a small number of mission-oriented exchanges, while TMX in high-quality includes both task-oriented exchanges and relationship-oriented exchanges [21] . Relationships of TMX in high-quality help build recognition, appreciation, encouragement, mutual respect, and trust among team members, while Relationships of TMX in low relationships result in lack of respect, trust, and team cooperation among team members [16] .

The meeting dimension of TMX means to effectiveness of team meetings. Team meetings are an important way for team members to share information, share ideas, make suggestions, and solve problems [5] . An effective meeting plan should clarify the purpose and goal of the meeting, indicate what views or suggestions are necessary, and play a guiding role in the meeting. The effectiveness of team meetings directly depends on the quality of the organization team. So, a meeting can be described as successful ones only after that it can motivate people to work hard, promote them to resolve conflicts through communication, encourage them to share opportunities, create crucial results, and leave with a sense of accomplishment.

When put in TMX context, exchange is a two-way reciprocal behavior between a member and a team [14] . That is, members spontaneously voluntarily provide support as well as feedback for other team members and share ideas them. In return, the member also received information, assistance, and recognition from team members [5] . In other words, exchange is acts of team members learning from each other and freely communicating feelings, ideas and opinions [22] .

Cohesion refers to a common sense of belonging, characterized by cooperation, group identity, commitment, and positive interdependence [23] . Tziner and Vardi (1982) proposed two forms of cohesion―sexual emotional cohesion with emotional satisfaction and goal-oriented tool cohesion [24] . Both kinds of cohesion are considered essential for efficient team work.

Seers (1989) believes that the above three dimensions together constitute the concept of TMX. He developed a measurement scale that contains 18 items, of which the exchange dimension has 10 items, and meeting and cohesion dimension each has 4 items [5] . However, Seers et al. (1995) argued in their future study that the exchange dimension is the most reliable predictor for measuring TMX concept [14] . Only this dimension is sufficient to explain the individual’s overall perception of the quality of the team’s working relationship. Therefore, in his study made by 1995, only 10 measurement items were used to measure TMX quality (see Table 1 for specific measurement items). Half of the 10 items examined the members’ contribution to the team, the other half examined the members’ support from the team. Apart from that, Seers et al. (1995) showed that the scale had good reliability and validity through doing pre-test as well as post-test. Later, the scale has been widely recognized and applied in TMX studies.

Although most of the research on TMX directly used Seers (1989) concept and his measurement scale, some scholars choose to modify and develop new scales basing on scale carried out by Seers (1995). For example, Chae et al. (2015) used scales that contain only three items adapted by Zhou and George (2001) from Seers’s 10 item scales. The scale includes questions like “I often asd other for help”, “Members on this team willingly suggest better work methods to others”, “Other members on this team recognize my potential” [1]. Monica Hu et al. (2012) used the scale of the 3 items developed by Alper, Tjosvold and Law (1998), like “Team members encourage each other to improve their work performance”, The high quality of the relationships in the team makes members enthusiastic about their work and the atmosphere keeps them focused on their work all day long”, “The interaction among team member is good” [25] .

Social exchange theory is a sociological theory that emerged in the United States in the 1960s and spread widely in the world. It advocates the study of social behavior theory from perspective of the relationship between input and output of economics [33] . This theory focuses on the attributes of interpersonal relationships and social interactions. It reconceptualizes interpersonal communication as a social exchange phenomenon, believing that seeking benefits and avoiding harm are the basic principles of human behavior. People tend to increase their benefits or satisfaction and reduce their costs or sacrifice during interactions,

which indicates that interpersonal communication is driven from “self-interest” [33] . The theory of social exchange, characterized by long-term unspecified obligations, argues that people are willing to socialize with people around in both their personal life and work. People temps to exchange trust, help, and feedback with each other [34] . Thus, theory of social exchange refers to a lasting interaction model that contains mutual debt responsibilities and commitments expressed in response to other individual needs, stemming from the informal relationship which generates trust and sense of obligation [35] . Social exchange theory can well explain the dynamic process of resource exchange between two or more people [36] . The theory holds the points that the higher the quality of workplace exchanges perceived by people, the greater their willingness to act altruistically in these relationships.

The theory of reciprocity originated from the social exchange theory [37] . Reciprocal norm, a potential core rule of social exchange relations, is widely used in the field of organizational research. Additionally, it is very crucial for research on employee incentives in organizations [21] . The reciprocity theory believes that people will try to respond in the same way to what others have done to them. For example, a member might participate in cooperation and do altruistic behaviors (such as positive reciprocal behaviors) as return to the support and help from others. Oppositely, they might respond by vengeance to the negative treatment they perceive [25] . At present, the types of reciprocity most widely acknowledged are generalized reciprocity, balanced reciprocity, and negative reciprocity [37] . Among them, generalized reciprocity refers to altruistic behavior, balanced reciprocity refers to equal returns in a timely manner and negative reciprocity refers to pursuing one’s own interests by harming other people’s interests without paying attention to give returns to others [15] . When it comes to organizational research, reciprocity, seen as a powerful incentive source, is one of the important factors that determine employees’ behavior [38] . Reciprocity can promote a high degree of consistency in collective action and motivate extra-role of behavior that favors organizational performance [39] . Therefore, TMX is a social exchange behavior based on the principle of reciprocity.

The role theory is a social psychology theory about how people’s attitudes and behaviors are influenced by their role in society and social role expectations. Being a branch developed from the theory of symbolic interaction, the role theory tries to explain and reveal the law of people’s behavior according to their status or identity [40] . Role theory holds the points that position of a person in social relationships determines a person’s social behavior, which also means that people’s social roles are played in the impact of social context [41] . The role theory mainly includes roles cognition, role learning and role expectations [40] . Roles cognition means that when in social organization activities, various social roles always tempt to interact with each other [42] . In a team, a team member’s understanding of self-behavior and status is based on his/her understanding of behavior and status from other team members. Role learning refers to the fact that every person might be assigned different rights as well as duties facing social organizational activities, indicating that one’s social role is constantly changing [38] . That’s why in the process of personal socialization, team members will continue to learn different social behaviors matched with various roles according to their cognition to their roles [42] . The so-called role expectation represents people temps to have a certain expectation of members from the organization because of his organizational positions [40] . In other words, role expectations imply that one gets expectations put forward by others in comply with one’s status and exert his/her understanding of such kind of expectations. In the team, individuals might get role expectations from their superior and coworkers. If individuals respond positively to and meet with these expectations, superior and coworkers might not only recognize individuals’ team membership, but also provide them with information, resources, feedback and assistance, which eventually help build high-quality TMX relationships.

Existing research on the far-end impact of TMX is mostly at the individual level. For example, through meta-analysis, Banks et al. (2014) found that individual-level TMXs can on the one hand improve team members’ job performance, job satisfaction, and organizational commitment. On the other hand, individual-level TMX can reduce team members’ willingness to turn over as well [13] . In addition, relevant research has also found that individual-level TMXexert positive influence on individuals’ organizational citizenship behavior [26] , innovative behavior [80] , the willingness to share knowledge [25] [70] and the socialization process after entering the organization. It can also ease individuals’ role of pressure [81] , reduce relationship conflicts and suppress the impact of job burnout [82] .

At present, there are few studies on the far-end effects of TMX relationships at the team level. Only a few scholars have discussed the output of TMX at team level. For example, Chae et al. (2015) pointed out that the higher the quality of TMX, the greater the willingness to share with, help and offer feedback to other team members, making team innovation performance as well as team effectiveness improved [1] . Liu et al. (2011) find that TMX positively related to team knowledge sharing, team commitment, and team performance [70] . Tse et al. (2008) show that high-quality TMX relationships have a positive impact on team effectiveness and team efficacy [21] .

There is not much research on the regulatory mechanisms of TMX, and most of them focus on the first stage of regulation (Figure 1). Firstly, at the individual level, studies by Monica Hu et al. (2012) showed that trust positively regulates the relationship between knowledge sharing and TMX [25] . To be more specific, mutual trust will not only motivate individuals to share knowledge, but also help build good colleagues relationship through reciprocity as well as feedback [25] . Therefore, the higher the degree of trust between individuals and team members, the more knowledge they are willing to share. In addition, Zou et al. (2015) found through research that TMX mediates the positive relationship between service leaders and helping behaviors towards colleagues, while individual reciprocal beliefs play a moderating role in service leaders and TMX. That is to say, when individuals’ reciprocal belief is high, the positive relationship between service leaders and TMX will be stronger, the positive relationship between service leaders and help-seeking behavior through TMX will be stronger as well. [18] .

At the team level, Tse et al. (2008) found that although high-quality LMX relationships produce high-quality TMX relationships for individual, level of LMXD will impact TMX too. The higher the level of LMXD, the lower the quality of individuals TMX relationships will be [21] . It is because the greater the difference in leader-member exchanges perceived by individuals, the stronger the sense of unfairness generated [7] , which in turn affects effective communication between team members. Even worse, high level of LMXD improve the tendency of

conflicts. What’s more, the research studied by de Jong et al. (2014) shows that the influence of negative relationships between team members on team cohesion can be regulated by task interdependency. The higher the level of task interdependence, the lower the destructive effect of negative relationships on team cohesion [32] . Therefore, similarly, high levels of task interdependence require team members to communicate, share and cooperate more related to tasks, which also help build good quality of TMX relationship. Based on optimal traits (ODT) of social identity theory, Farmer et al. (2015) points out that individuals have both assimilation needs (i.e., the need for collective identity and belonging) and differentiated needs (i.e., individual identity, uniqueness, and distinctiveness) and identification generated after two kinds of needs are met at the same time. The team’s high level of relative TMX (the relative TMX relationship with different members) can meet the individual’s differentiated needs while the high level of average TMX (the overall TMX relationship quality of the team) can meet the individual assimilation needs. Therefore, the interaction between the average TMX level of the team and the relative TMX level influences the individual’s team identity and colleagues’ identification, and thus affects the individual’s helper behavior [26] .

The research on the TMX second moderation mechanism is limited. Meta-analysis from Judge and Judge and Ilies (2002) shows that the three personality types in the Big Five personality traits―extroversion, neuroticism, and conscientiousness―are related to motivation output and process (i.e., self-efficacy, expectations, and goal setting) [83] . Liao et al. (2013) assumed that extraversion, neuroticism, and conscientiousness have an impact on the relationship between TMX and job participation. Empirical results show that extraversion is positive to moderate relationship between TMX and job participation. Besides, neuroticism as well as conscientiousness negatively moderate the relationship between TMX and job participation [29] .

In 1989, Seers defined TMX as an individual-level variable, reflecting the individual perception of the quality of the team’s work relationship [5]. Most of subsequent research also explored the mechanism of action of TMX from an individual level [13] . Seers, Petty, and Cashman (1995) pointed out that the promotion of TMX to the team level can reflect the quality of the working relationship within the team, which is also of great theoretical significance [14] . However, scholars have not reached an agreement on how to raise individual-level TMX to the team level. For example, some scholars believe that the TMX average can be used to measure team-level TMX. Some scholars believe that the TMX median should be used to represent the team level. Therefore, the definition as well as measurement of team-level TMX plays a critical role on the development of TMX theory. In addition, as described in the structural dimension section above, only the seers (1989) and Tse and Das borough (2008) have explored the dimensions of TMX so far. To clearly explain how the team-level TMX should be defined and measured, future research can be explored on TMX dimensions [14] .

Although many scholars have discussed antecedents as well as results of TMX from different perspectives, there are still many areas worthy of further exploration for the study of causes and consequences of TMX. For example, studies have shown that service leaders influence the quality of the team’s TMX. Will other leadership styles such as transactional leaders, transformational leaders, and ethical leaders also affect TMX quality? In addition, as for impact of TMX, most studies only focus on the direct relationship between TMX and individual-level or team-level output [13] , failing to clearly reveal its process mechanisms, especially lacking of attention to the interactive process of intra-team cooperation etc. Now it is still difficult to answer the question of how and when TMX influence individual or team. Therefore, in the future, it is also necessary to conduct in-depth discussions on the mechanism. What’s more, when it comes to causes of TMX, different scholars have various points. For example, Liu et al. (2011) believe that high-quality TMX relationship not only creates an atmosphere of mutual help and reciprocity, but also provides team members with more opportunities to share and communicate, making the interaction between team members more effective. It is more conducive to individual knowledge sharing [70] , while Monica Hu (2012) holds the points that individual knowledge sharing behavior will enhance his TMX relationship with the team [25] . It can be seen that the relationship between the antecedents as well as outcome variables of TMX is not clear yet, further research should be explored.