All of these questions pose very important answers. All of which I am prepared to answer and elaborate on.
Well, to start off, we do process most of our information outside of our conscious awareness. All of the sensory stimuli surrounding us on a day to day basis is being processed in our brains parallel to what we're selectively attented to. Actually, conscious processing lags behind the events in the brain. So, yes, we are affected by subliminal messages... to an extent. Here is an example of subliminal messaging:
Have you ever been in a class and completely tuned out a teacher in order to daydream? Did that daydream consist of a hypothetical situation in which you were hoping did or didn't happen? If so, you are completely normal. And this is no matter the content of the daydream, and I say this because sexual or vulgur fantasies do not indicate sexual problems or behavioral issues. Our daydreams simply provide us with a way of preparing for future events. It is not an escape, they involve the familiar details of our own lives. It can be adaptive and give us the opportunity to mentally rehearse possible scenarios. It is also scientifically proven to substitute for impulsive behavior.
Now, when it comes to sleeping and dreaming, many people are convinced that they do not dream at all. There are facts that will prove those people wrong. You see, there are 5 stages of sleep; Stage1, 2, 3, 4 and REM. As all of the stages of sleep are very vital to the sleeping process, psychologists tend to analyze a specific stage called REM, which stands for Rapid Eye Movement. REM, also referred to as paradoxical sleep, is the state of sleep in which your brain cortex is completely active and functioning but your brainstem blocks its messages to the muscles so you are essentially paralyzed. During REM, you dream. And only while in REM will you dream. REM dreams are very vivid and realistic. As to why some people claim that they do not dream and others dream 'every night', is the awakening during REM sleep. You will only remember a dream if you are awakened during the stage of REM.
You hear it all the time; 'You need sleep.' Ever truly wonder why we need sleep to function at our ultimate potential? The facts will be coming straight your way on the next post. :-)