The drowsy, trancelike state between sleeping and waking.During the hypnagogic period some people experience transient, dreamlike fantasies which have been termed hypnagogic hallucinations. Suggestibility is high during this state, and the sleeper may respond to a simple command such as “Raise your left arm,” or even mumble answers to questions. Experiments have shown that some individuals can retain vocabulary lists or other data read to them during this period. The increase in suggestibility which occurs in this twilight state seems to account for this ability to learn simple material