Temperament and regulation of emotion in the first years of life.

Temperament is the tendency to express particular emotions with a certain intensity that is unique to each individual child. Although temperament seems to be biologically based, learning to regulate emotional expressions depends on caregiver input and socialization. Part of this process involves forming a trusting relationship with the infant so that he or she learns to rely on the parents to help "regulate" stressful or frustrating situations.