Emotion and behavior are based on the child's developmental stage and temperament. Every child has an individual temperament, or mood. Some children may be cheerful and adaptable and easily develop regular routines of sleeping, waking, eating, and other daily activities. These children tend to respond positively to new situations. Other children are not very adaptable and may have great irregularities in their routine. These children tend to respond negatively to new situations. Still other children are in between.

At about 9 months of age, infants normally become more anxious about being separated from their parents. Separations at bedtime and at places like child care centers may be difficult and can be marked by temper tantrums. This behavior can last for many months. For many older children, a special blanket or stuffed animal serves at this time as a transitional object that acts as a symbol for the absent parent.

At 2 to 3 years of age, children begin to test their limits and do what they have been forbidden to do, simply to see what will happen. The frequent "nos" that children hear from parents reflect the struggle for independence at this age. Although distressing to parents and children, tantrums are normal because they help children express their frustration during a time when they cannot verbalize their feelings well. Parents can help decrease the number of tantrums by not letting their children become overtired or unduly frustrated and by knowing their children's behavior patterns and avoiding situations that are likely to induce tantrums. Rarely, temper tantrums need to be evaluated by a doctor (see Behavioral and Developmental Problems in Young Children: Temper Tantrums). Some young children have particular difficulty controlling their impulses and need their parents to set stricter limits around which there can be some safety and regularity in their world.

At age 18 months to 2 years, children typically begin to establish gender identity (see Sexuality: Gender Identity). During the preschool years, children also acquire a notion of gender role, of what boys and girls typically do. Exploration of the genitals is expected at this age and signals that children are beginning to make a connection between gender and body image.

Between 2 and 3 years of age, children begin to play more interactively with other children. Although they may still be possessive about toys, they may begin to share and even take turns in play. Asserting ownership of toys by saying, "That is mine!" helps establish the sense of self. Although children at this age strive for independence, they still need their parents nearby for security and support. For example, they may walk away from their parents when they feel curious only to later hide behind their parents when they are fearful.

At 3 to 5 years of age, many children become interested in fantasy play and imaginary friends. Fantasy play allows children to safely act out different roles and strong feelings in acceptable ways. Fantasy play also helps children grow socially. They learn to resolve conflicts with parents or other children in ways that help them vent frustrations and maintain self-esteem. Also at this time, typical childhood fears like that of "the monster in the closet" emerge. These fears are normal.

At 7 to 12 years of age, children work through numerous issues: self-concept, the foundation for which is laid by competency in the classroom; relationships with peers, which are determined by the ability to socialize and fit in well; and family relationships, which are determined in part by the approval children gain from parents and siblings. Although many children seem to place a high value on the peer group, they still look primarily to parents for support and guidance. Siblings can serve as role models and as valuable supports and critics in what can and cannot be done. This period of time is very active for children, who engage in many activities and are eager to explore new activities. At this age, children are eager learners and often respond well to advice about safety, healthy lifestyles, and avoidance of high-risk behaviors.

Last full review/revision May 2006 by Eve R. Colson, MD