Perceptual Illusion:

I chose ASMR, or Autonomous Sensory Meridian Response. ASMR is a perceptual phenomenon that causes pleasant tingling feelings in the head, back, and rest of the body. It can be triggered by auditory, visual, tactile, and other stimuli, but mostly is known for being caused by sound. 

An ASMR community has developed in recent years on the internet, and you can find many videos on Youtube dedicated to inducing ASMR in viewers/listeners made by "ASMR artists", or "ASMRtists". 

I chose ASMR as a perceptual illusion, because after I found ASMR videos a couple years ago I have always have been interested in how these artists could cause me to feel as though their hands and fingers were moving along my face and head, and how they caused tingling sensations within my head that allowed me to relax and fall asleep.

However, after reading up on it, I found that although people experiencing ASMR is well documented and agreed upon as a phenomenon, a solid scientific explanation has still not been found for it. There are many theories ranging from it being caused by secretions of the pineal gland, to it causing a psychological state similar to when people meditate. ASMR seems to be triggered by soft sounds, light touches, and positive personal attention.