Definition: Externalizing behaviors are actions that direct problematic energy outward. In other words, a person who shows externalizing behaviors does things that harm others as opposed to lashing out at the self (which are internalizing behaviors). Externalizing behaviors include physical aggression, verbal bullying, relational aggression, defiance, theft and vandalism.
Tweens show many externalized behaviors, especially when they are troubled. Boys are more likely than girls to show the more blatant externalized behaviors, like physical bullying, but on the whole, levels of aggression are similar between the sexes.
Related term: Internalizing behaviors
Phares, Vicky. Understanding Abnormal Child Psychology, Second Edition. 2008. Hoboken, NJ: John Wiley & Sons.