Humans are most comfortable with their eyes level with and on the horizon. When babies are lying on their tummies, they do not leave their foreheads on the ground to stare at the floor! Instead, each will upright the head in order to take in the world around him or her; this is precisely how the spinal curve of the neck begins to develop. Of course, infants will not be able to achieve full head uprighting at first, as this in itself is a 'skill' to develop. But even from a young age, the baby will look from side to side. Once a baby masters the ability to support the head, he or she easily will progress to a more difficult movement pattern - requiring head control - such as crawling or walking.