In the early stages of sleep, _____ waves appear.

The _____ theory of sleep says that sleep is a product of evolution.

Carmen stayed up all night studying, getting only about two hours of sleep total. While she was able to finish her exam, she was unable to focus, and much of what she had studied the night before seemed to be forgotten. Carmen's inability to remember and to stay focused during her exam is most likely due to

In studies in which volunteers spend several days without access to information about day or night, their sleep–wake cycles

Predators such as lions sleep _____ their prey, the gazelle.

Many researchers believe that reports of ghostly visions and alien abductions can be explained by _____ during N1 sleep.

The body is at its lowest level of functioning during _____ sleep.

Which of the following statements about REM sleep is true?

Nearly _____ percent of a baby's sleep is REM, compared to about _____ percent for a normal, healthy adult.