One way a hypnotist used to hypnotize people is by snapping a finger. When the finger is snapped after saying some words, the person immediately closes his eyes and gets into a trance.
Why is that so? The reason lies on:
The words of instruction by the hypnotist – The subject wants to be co-operative and simply follows the hypnotist’s instruction without fail.
The snap of finger is a cue for the subject to go into a trance.
It is more of a “want to co-operate” mentality that makes it works.