How can different sleep stages be manipulated or separated?

Answer 1

an alarm clock usually does the trick for me

Answer 2

There is no way at present to manipulate the different sleep stages, you can't force someone into REM or non-REM sleep at your will. There are some medications, such as barbiturates, which lead to a reduction in REM sleep, but this would not be an effective method of "manipulating" the different sleep stages.

As for separating, I take this to mean identifying. The different stages of sleep are measured using an electroencephalogram (EEG) and this wikipedia page shows you the different brainwaves that denote the different levels of sleep: http://en.wikipedia.org/wiki/Sleep#Sleep_physiology

One way to tell the difference between REM and non-REM sleep is that there is rapid eye movement (what REM stands for) in REM sleep but not non-REM sleep. Also, when people fall asleep for a very short time (10 seconds or so) and wake up immediately, denying that they have fallen asleep, they are in the first stage of sleep.

Answer 3

yes, you will find that in the text for psychology 101.