Suppose a stage hypnotist suggested that when you heard the opening bars of Beethoven’s Fifth Symphony, you would “go to sleep”. You are driving home from the show, and listening to Classic FM, and they play Beethoven’s Fifth. You begin to close your eyes and lose control of the car.
The problem here, as we shall point out later, is not cancelling the suggestion. It therefore acts as a posthypnotic suggestion. Why? Because the stage hypnotist says, “When you hear this” (and the music is then played), the suggestion is open-ended. It is not clear that it means only during this performance. The person being hypnotized may interpret the suggestion as meaning whenever he or she hears this particular piece of music. What we observe here is that suggestions given in trance can sometimes be interpreted as posthypnotic suggestions on the part of the person being hypnotized, even though the hypnotist did not mean it to be so. This is why common signals – whether actions, phrases or other signals – should be avoided at all costs.
When engaging in self-hypnosis, therefore, you must be careful. Avoid generalizations, like “When I snap my fingers I will bark like a dog”. This is something you would not like to do at a meeting when you happened to snap your fingers! What you want to say is, “When I next snap my fingers I will bark like a dog”. This is specific and not general and involves only the next act of snapping your fingers and not all future occasions. Of course, “barking like a dog” is a silly suggestion, but it illustrates the importance of being careful about giving posthypnotic suggestions even to yourself.
One way to avoid common phrases or actions is to combine a phrase and an action – where these would never occur together in common usage or by accident. In this case both the action and the phrase can be simple and of common usage, but would not occur together. Whatever signal you choose, the posthypnotic suggestion should make it absolutely clear that you will respond only when you yourself give it. Although this may have been assumed, it is much safer to incorporate it into the suggestions so that there is no doubt as to what you are expected to do. In other words, you will carry out the posthypnotic suggestion only when you yourself give the signal.
When giving a posthypnotic suggestion it is necessary to constantly repeat the signal. It should also include a safeguard so that it is not accidentally carried out in other circumstances in which it was not meant to. With some individuals a posthypnotic suggestion is long lasting while with others it wears off. Why is not clear. Repeating the posthypnotic suggestion at intervals, however, will reinforce it.