The objectives of this study were to examine the influence of bystanders' perceived reasonableness of online messages on their aggressive tendency toward victims and to examine the mediating role of bystanders' attribution of responsibility to victims on their aggressive tendency toward the victims. Our study involved two parts: In Study 1, 295 Taiwanese undergraduates were recruited, and questionnaires were distributed to them to measure their perceived reasonableness of cyberbullying attacks. In Study 2, a total of 78 university students were recruited. The participants' perceived reasonableness of cyberbullying attacks was reduced through experimental manipulation. Subsequently, they were randomly assigned to a group with relatively low reasonableness or a control group. The results of both studies revealed that the participants' aggressive tendency toward the victim was influenced by their perceived reasonableness of cyberbully messages. The relation between perceived reasonableness and aggressive tendency was mediated by the participants' attribution of responsibility to the victim.
Keywords: aggressive tendency; attribution of responsibility; bystander; cyberbullying; perceived reasonableness.