Schlegel and Barry (1991) found that what percentage of adolescent boys and girls had frequent responsibility for caring for younger siblings in traditional cultures?

What percentage of infants are currently breast fed in the United States and Canada?

a. 10% b. 40% c. 70% d. 99%

According to Piaget, infants do not have a full understanding of object permanence until

a. 6 month of age. c. 12 months of age. b. 9 months of age. d. 18 months of age.