10 Explanations For Those Strange Things You Do All The Time
8. Why Do I Always See Things Out Of The Corner Of My Eye?
Your eyes can definitely play tricks on you, particularly when its 4am and you've spent all night marathoning American Horror Story, at which point every shadow is some servant of Satan come to pull you to hell.
The way you perceive the world isn't necessarily true to life. Both your eyes and your brain are imperfect tools, and so a fair bit of tweaking goes on to "fill in the blanks".
Your peripheral vision is not very good at sharp focus, but it is very good at detecting movement and shapes - that's basically what it's there for, to ensure you can spot a lion before it eats you.
Natural selection will have played a part in ensuring that the people with good peripheral vision (and an over-active imagination to go with it) will have survived better because their brains are primed to spot threats - even if sometimes it's only the grass blowing in the wind. It's better to imagine a threat when there isn't one, than ignore on when there is.
So, the next time you spot a demon in the corner of your room, only to turn and see that it's just your dressing gown hanging on your door, it's just your brain's way of keeping you safe.
Either that, or demons are just really good at disguising themselves as dressing gowns.