We found that young children, up until about 7 years old, think that one person is right and another is wrong. It is only when children are a little bit older that they think in terms of people wanting different things. Cognitive maturity also influences their understanding of a resolution. Young children think that conflicts are over when angry behavior and angry expressions stop. The emotion system developed as a system that monitors the status of our goals during our transations with the environment.
Emotions signal to the self and the other the nature of the individual's goals.
Happiness signals goals of cooperation and affiliation. These individual differences in emotion expression are important in how we understand personality and psychopathology. We have found that children with acting out or externalizing disturbance show a lot of anger expressions, but few happiness or sadness expressions when interacting with other children. Children with internalizing disturbance including depression show a lot of sadness but very little anger. I will be dominant and retaliate.