The first film of the Tactile Anchoring Device in progress, showing the use of brushes and fans to generate the illusion of an invisible hand... https://youtu.be/vHaB6HBbQrs The system is based on an Arduino controls two sets of identical stimuli which move in synchronisation with each other [ servo motor, articulating solenoids, fans, lamps etc] Once the participant is experiencing the illusion, the operator or autonomous systems can trigger a ‘shock’ or threat stimuli. This is currently in the form of a solenoid which releases a heaved plum line weight which drops into the empty space. See the project page here. http://antonyhall.net/blogtactile-anchoring-device/