I like to call Stage 1 “boring lecture sleep” because it’s the state most of us are in when we’re a bit tired and sitting through a boring lecture: Our eyes close and we hear the speaker droning on only in the distant background. Stage 1 is actually a transitional stage of sleep in which you begin to disconnect from your surroundings and start moving into a nonwakeful state. While you may still feel attached to your environment—you know you’re sitting in a lecture hall listening to a boring speaker—you also may experience a sense of sleepiness or fading.

Stage 1 sleep generally lasts about 10 minutes, and you can be awakened from such sleep fairly easily—often accompanied by that embarrassing full-body, falling-off-the-cliff jerk. Many people who wake up from Stage 1 will deny that they were really sleeping, even when you’ve been watching them twitch and snort and breathe more slowly.

Brain waves in Stage 1 are characterized by a gradual waning of the 8- to 12-cycles-per-second alpha wave rhythm that is the hallmark of relaxed wakefulness and an increase in slower, four- to seven-per-second theta wave forms that indicate sleep. Slow, horizontal roving-eye movements may be seen during this stage of sleep, and there may also be a regularization of breathing and a slight relaxation of the muscles. During the transition to Stage 1 from wakefulness, some people experience visual misperceptions called hypnogogic, or drowsiness-related, hallucinations. Others experience what they describe as a feeling of falling.