Jasmine is fascinated by the jingling of a ring of keys her mother has. when her mother drops the keys on the table behind jasmine, the infant starts to cry and moves her hands in protest. this shows that jasmine has not developed an understanding of:

Jasmine has not developed an understanding of object permanence. 

Object permanence refers to ability to perceive and understand that an object continues to exist even if it is covered, moved or no longer in sight. Jasmine has not developed an understanding of object permanence since she seems to believe that the ring of keys no longer exist once their were no longer in her sight (when her mother dropped them on the table behind Jasmine). This is why Jasmine cries when an object she likes appears to "vanish".