Wooden Hippo RattleOne of the earliest skills infants begin to pick up is eye tracking. Sometime after the newborn stage, infants will start to look for and track the sources of sounds they hear. Understanding that objects can make sounds is an early lesson in cause and effect. Ideas for play: Shake the rattle near your babys face to capture her attention. Keep shaking while moving it past their eyes and they start tracking the sound with their eyes.