Sleep brain waves and lifespan changes in sleep and wakefulness: In chart A, you can see the EEG patterns associated with the four stages of sleep that first appear during adolescence. After we fall asleep, our brain waves get progressively slower (these are the four stages of non-REM sleep) and then we enter the REM phase during which dreaming is intense. Now, notice in chart B the time young babies spend in REM. As REM sleep helps consolidate memory, is the incredible time babies spend in this phase crucial to absorbing the overwhelming amount of information that must be mastered during the first years of life?

Adapted from: Roffwarg, Muzio, & Dement, 1966.