Our surroundings can easily influence our dreams
While we sleep, we have a lot of physical factors around us that can directly affect how our dreams play out. Some of the external factors that can influence our dreams are the sounds around us, what we smell, our posture, our psychological state, medications and vitamins, and the absence of something (like if you were on a diet or if you quit smoking). While we are in the REM stage of sleep, these factors can affect our dreams both negatively and positively.
External factors that can directly affect how we dream
Sounds can be incorporated in our dreams
If you have the television on in the background while you're asleep, chances are you'll be able to hear it in your dream. Researchers have found that sounds from cars, television, and even your alarm clock can also make an appearance while you are sleeping.
Scents can affect the emotions you feel while dreaming
Depending on what smells are around you, you can have positive and negative emotions. German researchers actually studied the amount of influence scents can really have on our emotions. While in REM sleep, participants had to either smell something sweet, like roses, or something bad, like rotten eggs. In this experiment, the participants who had a positive impact on their dreams were the ones who smelled the roses, and the ones who had a negative effect smelled the rotten eggs.
Sleeping on your stomach can also have an effect on your dreams
A study in China recently demonstrated that people who sleep face down and on their stomach typically have erotic dreams or dreams that someone is stalking them. Another effect your posture can have on your dreams is that we remember them better if we remain in the same position when we wake up.