He Remembers! Infants are fascinated by moving objects within a few feet of their eyes–that’s why parents buy mobiles for cribs, and why Rovee-Collier tied a string to a mobile and a baby’s leg to test memory. Babies not in her experiment, like this one, sometimes flail their limbs to make their cribs shake and thus their mobiles move. Piaget’s stage of “making interesting sights last” is evident to every careful observer.