We can all relate to needing sleep, and most of us know all too well what it feels like when we have not gotten enough of it. First, read about our circadian rhythm and what influences it.
Circadian Rhythm
It is clear that sleep is necessary for replenishing our resources. This includes our cognitive resources. Bodenhausen (1990) found that we use stereotypes more when we are not in the optimal time of our circadian rhythm. Bodenhausen's study asked participants to make judgments about other people. People who identified themselves as a "morning person" used more stereotypes when asked to make these judgments at night. "Night people" used more stereotypes when they were judging people in the morning. This fits with what we know about heuristics. We use shortcuts in judgment to preserve cognitive resources. We have fewer resources when we are not in an optimal time of our circadian rhythm.
Read: Circadian Rhythm Fact Sheet (http://goo.gl/ScT5eh)
Next, watch this video so you are familiar with the five stages of sleep and what happens in each:
Watch: 5 Stages of Sleep (http://www.youtube.com/watch?v=qEWbu37fH9k)
How does alcohol affect our sleep cycle?
Watch: How Alcohol Affects Your Sleep (https://youtu.be/hYVTTvJ8J3s)
What is poly-phasic sleep?
Contrary to popular belief, there is not one "healthiest" way to sleep throughout the day/night. Some people sleep better by not lumping all of their sleep into one 8-hour block overnight, but rather, sleeping in smaller chunks of time (sometimes during the day).
Read: Nightly 8-Hour Sleep Isn't a Rule. It's a Myth.