The relationship between in-group favoritism and online prosocial behaviors among college students: the role of moral self and the belief in a just world

Objective This study aims to explore the joint mechanism of in-group favoritism and belief in a just world on individual online prosocial behaviors among college students in the context of online donation, with a focus on the mediating role of the moral self and the moderating role of belief in a just world. Method A online donation scenario was created through experimental methods to manipulate participants' in-group favoritism (high vs. low) and belief in a just world (priming group vs. control group). Their moral self-level and online prosocial behavior (using comment word count as an indicator of expressive prosocial behavior) were measured. Results (1) In-group favoritism significantly and positively predicted online prosocial behavior; (2) The moral self played a significant mediating role between in-group favoritism and online prosocial behavior; (3) Belief in a just world moderated the influence of in-group favoritism on the moral self. Under the condition of activated belief in a just world, the positive predictive effect of in-group favoritism on the moral self was stronger, thereby indirectly affecting prosocial behavior through the moral self. Conclusion The present study found that the moral self serves as an internal psychological mechanism through which in-group favoritism influences online prosocial behavior, and that belief in a just world moderates this mechanism. These findings provide a new theoretical perspective for understanding the driving factors of prosocial behavior in online contexts and offer practical implications for guiding college students' online prosocial behavior.