Children acquire many skills as they grow. Some skills, such as controlling urine and stool, depend mainly on the level of maturity of the child's nerves and brain. Others, such as behaving appropriately at home and in school, are the result of a complicated interaction between the child's physical and intellectual (cognitive) development, health, temperament, and relationships with parents, teachers, and caregivers (see also Childhood Development). Other behaviors, such as thumb sucking, develop when children look for ways to help themselves cope with stress. Still other behaviors develop in response to parenting style.