While illusions may occur with any of the human senses, optical illusions are the best known and understood. 
That’s because vision often dominates the other senses. For example, as psychtalkradio explains, individuals watching a ventriloquist will perceive that the voice is coming from the dummy because they see the dummy mouthing the words.
Technically, the term “illusion” refers to sensory distortion in reaction to a stimulus. In other words, the brain uses general assumptions to decide what it is seeing, which may be completely different from what is real. When someone is hallucinating, on the other hand, they perceive something when there’s no stimulus (hearing voices when there’s no one there, for example).
Psychological illusions can be fun. That’s a big part of what makes date night at a Mind Tripping show so enjoyable a way for couples to share surprises and watch each other’s reactions. But our brains can trick us in many ways. Auditory illusions, for instances, trick us with sounds into making the wrong connections. Movie and video producers use audio illusions all the time.
In a clip called “Virtual Barber Shop”, we hear tones being played in higher and higher octaves. In reality, however, the same sounds keep repeating, with multiple octaves playing over and over at the same time. This phenomenon, composer and producer Charlie McCarron explains, is called the Shepard tone illusion. Since our brains love continuity and pattern, we follow the melody up into the next octave when actually the same combination of sounds is repeating.
Auditory illusions are very, very common, with a sound seeming louder, softer, fainter, or more distinct than it really is. A sound may also seem to be repeating more times than it really does (the Doppler effect).
When people come to see Christian and Katalina for the first time, they often don’t know what to expect. But very soon, they come to realize that Mind Tripping is a really fun night together even if they can’t explain everything they see. Psychological illusions can be absolutely awe-inspiring. The mind tripping takeaway – don’t believe everything you hear or see!
– By Opti of the Mind Tripping Show blog team