Prenatal 1( ) experience may contribute to postnatal attachment in human babies as shown by the 2( ) experiment. Newborns indicated their preferences in this study by altering their rate of 3 ( ) to control the stimuli. Prenatal 4 ( ) experience may also contribute to postnatal attachment in infant rate. Their First 5 ( ) response is guided by cues from 6 ( ). During the first postnatal week, rate pups acquire preferences for familiar odors paired with 7( ) stimuli. However, by the end of the second postnatal week, they show preferences for odors paired with 8 ( ) stimuli. This change may reflect maturation of the 9( ) system which stimulates early 10 ( ) learning.