Ch 4 - Infancy: Physical Development

The head of the newborn child doubles in length by adulthood, but the legs increase in length by about five times.

• Truth

• Fiction

Answer explanation

This is true. The torso also increases by about three times and the arms by four times.

Infants triple their birth weight within a year.

• Truth

• Fiction

Answer explanation

Truth. They usually double their birth weight in only five months.

A newborn's brain weighs about 25% of its adult weight, but grows to some 70% of its adult weight by the child's first birthday.

• Truth

• Fiction

Answer explanation

It is true that a newborn's brain weighs about 25% of its adult weight, and that it mushrooms to some 70% of adult weight by the age of one year.

The cerebral cortex -- the outer layer of the brain that is vital to human thought and reasoning--is only one-eighth of an inch thick.

• Truth

• Fiction

Answer explanation

This is true. Look at a ruler and think about that for a while.

1.         Native American Hopi infants spend the first year of life strapped to a board, yet they begin to walk at about the same time as children who are reared in other cultures.

• Truth

• Fiction

Answer explanation

Truth. It is true that Native American Hopi infants spend the first year of life strapped to a board yet begin to walk at about the same time as children who are reared in other cultures. This finding is strong evidence of a powerful role for maturation (4-3c).