Final answer:
Temperament refers to inborn, genetically based personality differences that influence how one thinks, behaves, and reacts with the environment. Newborn infants can be categorized into three temperaments: easy, difficult, or slow to warm up. Environmental factors and maturation can affect the expression of a child's temperament.
Step-by-step explanation:
Temperament refers to inborn, genetically based personality differences that influence how one thinks, behaves, and reacts with the environment. Studies by Thomas and Chess categorized newborn infants into three temperaments: easy, difficult, or slow to warm up. Environmental factors and maturation can also affect the expression of a child's temperament.