Aggression can a problem for children with both normal development and those with psychosocial disturbances. Aggression constitutes intended harm to another individual, even if the attempt to harm fails (such as a bullet fired from a gun that misses its human target). There is no single theory about the causes of aggressive behavior in humans. Some believe aggression is innate or instinctive. Social theorists suggest the breakdown in commonly shared values, changes in traditional family patterns of child-rearing, and social isolation lead to increasing aggression in children, adolescents, and adults. Aggression in children correlates with family unemployment, strife, criminality, and psychiatric disorders. Differences exist between levels of aggression in boys and girls in the same families. Boys are almost always more aggressive than girls. Larger children are more aggressive than smaller ones. Active and intrusive children are also more aggressive than passive or reserved ones. Aggressive behavior may be intentional or unintentional. Many hyperactive, clumsy children are accidentally aggressive, but their intentions are compassionate. Careful medical evaluation and diagnostic assessments distinguish between intentional behaviors and the unintentional behaviors of emotionally disturbed children. Children in all age groups learn that aggressive behavior is a powerful way to communicate their wishes or deal with their likes and dislikes.