Behavioral homophily, problem behaviors in particular, has also been extensively investigated in the past decade show that children with externalizing behavior problems (e.g., aggressive, disruptive, or defiance behaviors) tend to affiliate with peers sharing similar externalizing behaviors. Moreover, recent evidence suggests that children with internalizing behavior problems, namely, directing distressing feeling toward the self and consequently experiencing “sorrow, guilt, fear, worry” tend to befriend other internalizing peers, after controlling for externalizing behaviors and gender effects.