This is a light sleep when dreams occur and the eyes move rapidly back and forth. Although babies spend about 16 hours each day sleeping, about half of this is in REM sleep. Older children and adults sleep fewer hours and spend much less time in REM sleep. These cycles may occur several times during sleep. Babies may awaken as they pass from deep sleep to light sleep and may have difficulty going back to sleep in the first few months.
Babies also have differences in how alert they are during the time they are awake.
When a newborn awakens at the end of the sleep cycles, there is typically a quiet alert phase. This is a time when the baby is very still, but awake and taking in the environment. During the quiet alert time, babies may look or stare at objects, and respond to sounds and motion. This phase usually progresses to the active alert phase in which the baby is attentive to sounds and sights, but moves actively. After this phase is a crying phase.