Abstract:

Numerous studies have discussed the inducing factors of aggression, among which social exclusion has been widely concerned as a strong predictor. However, the studies about the association between social exclusion and aggression have shown mixed results. Theoretically, there are two main arguments about the relationship between social exclusion and aggression. The general aggression model suggests that social exclusion triggers negative emotions, hostile cognition, or a high level of physiological arousal, which leads to aggression. While the emotional numbness hypothesis argued that social exclusion causes individuals to be a state of physiological or emotional numbness, which may buffer the aggressive impulses. Empirically, the effect sizes of this relationship reported in the existing literature were far from consistent, with r values ranging from −0.02 to 0.74. Therefore, this meta-analysis was conducted to clarify the strength of the relationship between social exclusion and aggression and reveal possible moderators.

A systematic literature review was conducted using Web of Science, Elsevier SD, Medline, EBSCO-ERIC, SAGE Online Journals, PsycINFO, PsycArticles, ProQuest Dissertations and Theses, CNKI (China National Knowledge Infrastructure), WFD (Wan Fang Data) and CQVIP Journal Database.The literature screening process is shown in Figure 1. A total of 92 studies (99 independent effect sizes, 65564 participants) met the inclusion criteria were selected. A random-effects model was selected to conduct the meta-analysis in Comprehensive Meta-Analysis 3.3 software, aiming at testing our hypotheses. The results of heterogeneity test illustrated that there was significant heterogeneity among 99 independent effects. Based on the funnel chart and Egger’s regression test of intercept, no significant publication bias was found.

The results of main effect analysis indicated a significant positive correlation between social exclusion and aggression (r = 0.38, 95% CI [0.34,0.41]). Table 1 showed the results of moderator analysis, which revealed that the association between social exclusion and aggression was moderated by age, research methods, aggression types (reactive aggression vs. proactive aggression), social exclusion and aggression measurement tools, and research design (cross-sectional study vs. longitudinal study), but not by individualism index (b = −0.0012, 95% CI [−0.0026, 0.0002]) and gender (b = 0.10, 95% CI [−0.20, 0.40]).

The results of this meta-analysis can clarify the controversy of the correlation between social exclusion and aggression, indicating that excluded individuals are often accompanied by the increase of aggression level. Future research are encouraged to strengthen the prevention and intervention of aggressive behavior caused by social exclusion among low-age groups, especially preschool children and primary school students.

Key words: social exclusion, aggression, aggressive behavior, meta-analysis