## 2 Theoretical Background and Hypotheses
### The Moderating Role of Experience  
Experience is a critical factor that has an important influence on some key constructs and relationships (e.g., [48; 49]), because experience increases one's understanding about the actual performance of a service or an information technology [13]. According to the self-perception theory [13; 50], an individual will adjust his/her perceptions by observing the outcome of focal behavior, and the adjusted perceptions will impact subsequent behaviors. Researchers also find that social support will be facilitated when one's online contacts increase over time [25; 51]. Accordingly, we propose that the influence of online support on subjective well-being may change as experience increases over time.  
According to [25], the size of a social network in an online setting is related to one's perception of social support and thus affects his/her perception of well-being. This implies that users may not obtain sufficient help and support from others, as a result of being in a small-sized social network and having weak online social ties at the beginning of social media usage. In addition, from the viewpoint of the social exchange theory [52], helping others and responding to others' needs in the online context could be considered a social investment [23], as people expect that they could receive help from others in the future [35; 53]. This means that helping others is particularly important for users with low levels of experience, because it will allow them to increase self-identity and thus increase social interactions with others, to receive help from others in the future. Based on the aforementioned arguments, we recognize that users with low levels of experience will be more likely to be involved in providing online support activities than those with high levels of experience. Hence, we propose that providing support to others will cause higher-level perceptions of well-being for users with low levels of experience.  
**Hypothesis 5 (H5)**.: _The link between receiving online support and subjective well-being will be stronger for users with high levels of experience than that for users with low levels of experience._  
As the density of social relationships increases through interactions over time, users will have a better understanding of each other and thus promote the development of shared values and shared identities [54]. At this stage, people will also make emotional investments in relationships among members and express genuine care and concern for the welfare of others [55; 56]. A high social network density at this stage may enable people to appreciate others' desires [55] and trigger more effective and value-adding resource exchanges among users [54]. Accordingly, users with high levels of experience may acquire more valuable resources and better emotional support from others than those with low levels of experience. Receiving more valuable resources and support may lead to higher levels of perception of well-being. Therefore, we propose the following hypothesis.  
**Hypothesis 6 (H6).**_The link between providing online support and subjective well-being will be stronger for users with low levels of experience than that for users with high levels of experience._  
Based on the above arguments, we propose a research model, which is shown in Figure 1.