Ages and Stages

Chronological age is an important tool used by individuals, families, psychologists, and even government agencies to mark progress through the lifespan. Parents, physicians, and family members monitor the fetus’s development through each week in a pregnancy; once the baby is born, families celebrate each passing year with cake and candles. School systems use chronological age as a measure of eligibility for school entry, and governments use age to determine eligibility for benefits and social responsibilities and privileges (although not all teenagers wait until their 21st birthday to enjoy their first cocktail!).

But age is more than a chronological number that marks the number of years since we made our debut in a delivery room. Rather, age is associated with various biological, psychological, and social developmental milestones ...