The research of Spelke and research of Baillargeon show that infants as young as 3 or 4 months old understand object permanence because infants expect them to exist when the objects are hidden. However, critics question whether an infant's _____ is a valid measure of object permanence because it merely demonstrates ______.
A. lack of interest in the objects; cognitive competencies
B. lack of interest in the objects; perceptual competencies
C. longer looking time; perceptual competencies
D. longer looking time; cognitive competencies