Fear of darkness is as old as darkness itself and as varied as the people who are afraid. Everyone can remember a time (I want to write in childhood but I still experience this) when you dread going into that dark, dank basement or having to shut the closet door before going to sleep in fear of the blackness and whatever maybe waiting…inside. Fear of the dark is one of the few things that are both rational and irrational, sometimes at the same time. Being in the dark makes one vulnerable to their environment, there is not doubt about this, but are the things to which you are vulnerable real or imagined? This is a good question but never the less irrelevant. Fear whether real or just the workings of an imagination is an actuality, handed down from generation to generation, which makes it timeless. Before we consider why we are frightened of the dark, let’s review how we fear. 
1. It all starts in the brain (but don’t most things), in a section called the Hippocampus. The hippocampus forms our day to day experiences into memories. These memories are then sent to the amydgala.
2. The amygdala is a “store house” for good and bad memories (created by the hippocampus), experiences and emotions. The amydgala takes the stimuli from our real world information to our environment and sends signals to other areas of the body, resulting in appropriate emotional and physical responses. Physical responses which occur due to amydgala signaling are: dilated pupils, increased heartbeat, hyperventilation, nausea, bladder restricts, bowels slow down and an increase in blood pressure. On the “dark side” of amaydgala’s work, this is also the starting point of phobias. Phobias can start in this section of the brain because the amydgala operates unconsciously, so it can be prone to errors in its interpretation of the information it collects.
3. Signals from the amydgala reach the hypothalamus and triggers changes in the hormones the body produces. These changes get the body ready to take action in response to the emotions stimulated: “fight or flight,” crying, laughing, or for the purposes of this topic, muscle contraction so you can run.
Now that you understand how you are afraid physiologically, the next two posts will discuss why you are afraid. These should be much more interesting to the folks who couldn’t care less about brain functions.
Carter, R., Aldridge, S., Page, M., Parker, S. “The Human Brain Book,” 2009
http://www.dana.org/news/brainhealth/detail.aspx?id=10068
The History Channel “Afraid of the Dark,” aired 2010
