In sum, this study explores whether and how college students' activities related to communicating about sports on social media and face-to-face communication with heterogeneous people can be associated with their levels of group identity and collective self-esteem. It also examines whether gender and ethnicity differently influence students’ formation of group identity and collective self-esteem, especially when they communicate with heterogeneous others.

Another important question this study tackles is how demographic characteristics or social groups (e.g., gender and ethnicity) come into play in the relationship between college students' communication activities and their group identity and collective self-esteem. Diversity in a campus is always an important matter in the United States. Research has shown that college enrollment rates are different depending upon gender (Lopez & Gonzalez-barrera, 2014) and that enrollment rates for White students' are significantly higher than for students of other ethnic groups (Camera, 2015, Casselman, 2014). In the present campus environment in the United States, it is important to explore whether or not all students are able to easily interact with various and heterogeneous people and to form group identity and collective self-esteem. However, it remains unclear whether both male and female students and White and non-White students are likely to often engage in communication network heterogeneity and to increase group identity and collective self-esteem. In order to expand the scope of the literature on diversity, this study explores the moderating role of students’ gender and ethnicity in the relationship between communication network heterogeneity and group identity and collective self-esteem.

Social media boost users' communication network size and diversity as they interact with other users from diverse backgrounds. This might also be the case among college students when they post and share school-related sports information on social media (Boehmer and Lacy, 2014, Haugh and Watkins, 2016, Waters et al., 2011, Witkemper et al., 2012). As yet, little is known about whether and how students' interaction about college sports on social media can be linked to face-to-face communication network heterogeneity in daily life, which may further be associated with college students' group identity and collective self-esteem. This study therefore contributes to the current literature by empirically investigating the role of online and offline communication activities (i.e., social media use for sports-related events and face-to-face communication heterogeneity) in the formation of college students’ group identity and collective self-esteem.

This study explores a mediating mechanism by which social media use to talk about sports indirectly influences college students' group identity and collective self-esteem via communication network heterogeneity, which is defined as the degree to which individuals communicate with heterogeneous others. Social identity theory suggests that individuals develop themselves to be a member of a certain group and become more socialized in a social group as they routinely communicate with diverse people within the social group (Tajfel & Turner, 1986). This study acknowledges that social media use for college sports might play an important role in influencing individuals’ group identity and collective self-esteem by facilitating offline interaction with heterogeneous others.

This study especially focuses on college students' communication activities on social media that might positively influence their group identity and collective self-esteem. For college students, in particular, social media have become deeply rooted in daily life, allowing users to share a variety of campus life-related events and issues (Ellison et al., 2007, Lenhart and Madden, 2007). Recognizing the impacts of interaction on social media, universities offer diverse news about the university on social media, and students indeed actively use social media for school work and many other aspects of their college life (Nández & Borrego, 2013). The use of social media has become a popular way for sports fans to enjoy sports events by posting and talking about the events and to connect to athletes and other sports fans (Kim, Liu, & Shan, 2017). Because engagement in sports can be an instrument for individuals to identify with other members of a community (Anderson & Stone, 1981), the current study expects that college students' social media use related to college sports will be associated with their group identity and collective self-esteem. This may be especially true given that college students share their common experiences and feelings about their own university's sports events with other friends and colleagues on social media platforms.

The university is an important venue where students learn about not only academic knowledge but also humanity. During campus life, how college students grow as social beings before entering society is an important matter (Tajfel and Turner, 1986, Turner, 1999). According to social identity theory, individuals classify themselves as who they are and develop themselves to become more socialized in a tangible or symbolic social group (Tajfel & Turner, 1986). Acquiring feelings of group identity and collective self-esteem, generally defined as the degree to which individuals feel closely tied to their groups and the extent to which they evaluate their social group positively, respectively (Crocker and Luhtanen, 1990, Tajfel and Turner, 1986), is essential to cultivate personal development as social beings and is strongly related to psychological well-being (Graham-bailey, Cheeks, Blankenship, Stewart, & Chavous, 2018).

Although prior studies have examined the consequences of group identity and collective self-esteem, including individuals' psychological well-being, life satisfaction, depression, interpersonal relationships, media use, and so forth (Barker, 2009, Crocker and Luhtanen, 1990, Martiny and Nikitin, 2018, Zhang et al., 2011), relatively little research has empirically explored what influences college students' group identity and collective self-esteem. This study, therefore, aims to fill this gap by investigating whether and how online and offline communication activities are related to college students’ group identity and collective self-esteem.