Have you ever gotten a glimpse of something out of the corner of your eye? A simple movement caught in your peripheral vision. Most will simply dismiss this as a shadow brought about by a flickering candle, or perhaps a pet jumping down from a piece of furniture.
But then there's that one elusive sight. It can easily be explained by the above conditions, but something feels wrong about it. A chill down your spine, a slight pain in your side. Maybe even a complete blanking of your mind, only to recede moments later.
Should any of these symptoms be felt, there may be cause for worry. Our peripheral vision is designed to catch motion, even in the dark. This was used to defend against predators in our early days, and as with many aspects of our human nature, it has remained, but weakened. This view out of the corner of our eyes still alerts us to danger, and although predators have dropped on the list of dangers we may face today, they still exist.
Should you ever feel that queer chill in your back, try not to focus on that shadow you saw in the corner of your eye. It might be better not to see.