Introduction to Psychology 10th Edition by Rod Plotnik,Haig Kouyoumdjian

Exercise 16

Researchers divide sleep into five stages. Stage 1, the transition from wakefulness to sleep, is marked by (a) _____waves and a feeling of gradually losing responsiveness to the outside world. Stage 2 represents the first real phase of sleep and is marked by high-frequency bursts of brain activity called (b) _____. In stage 3 and especially stage 4, there are high-amplitude, low-frequency brain waves called (c) _____k. Stage 4 may be considered the deepest stage of sleep, since it is the most difficult from which to wake someone. Together, stages 1, 2, 3, and 4 are referred to as (d) _____sleep, which makes up about 80% of sleep time.