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After having examined (optical) illusion and misdirection, we come to the final part of how the magician, illusionist or con artist works their "magic" - convincing us to convince ourselves that the magic is real. For the most part, "fooling ourselves" is part of leading the audience with misdirection, until they come to a conclusion that supports the trick.
In magician terms, this is know as "The Force" (or in confidence games "The Hook"), and is best exemplified by fortune telling and horoscope. The fortune teller's art is to provide a vague description and fortune that can fit just about any situation. As long as the participant wants to believe, they'll find a situation that makes the fortune true - for example, "You will meet a tall, dark stranger" may be successfully fulfilled by meeting your child's handsome teacher, yet in the absence of such obvious confirmation, just about any encounter will do - "Well, that guy that crossed my path at the checkout was... maybe... kinda tall, had... oh, a bit of a tan... I suppose he could be called handsome... well, he wasn't ugly..." [This, by the way, also partially explains "coincidence" and "deja vu" in which what we think we experience, is partially filled in from memory and association!]
One of the most successful - although least obvious to a novice - tricks in a magician's repertoire is the Force. Through the Force, an audience member seemingly makes random or free choices, but the magician subtly guides that choice in the direction necessary for the trick. Not to give away any secrets, but an obvious application is used in confidence games where the operator questions a correct choice with "Are you sure? Are you really sure?" in order to get the "mark" to change their selection from correct to erroneous. In card magic, a Force is used to guide the audience member's choices to keep narrowing down the possible combinations - for example, cards are laid out in rows and columns, the participant makes a choice of row, the cards are "shuffled" and replaced, then the participant makes a choice of column. A skillful Force can that only one card can fulfill all of the possible choices.
A combination of illusion, misdirection and Force is also something that I have successfully used when performing card magic - the first several tricks are performed according to the rules that I establish, with my card decks, and a bit of setup. About the time the audience begins to suspect that my card decks are rigged, I challenge the audience to provide a deck of their own choosing (this worked especially well with Boy Scouts at summer camp - someone always had their own deck of cards), I then smoothly shift to tricks that work well with any deck, and leave the audience scratching their heads - all with a subtle manipulation of misdirection and Force.
The practice of "filling in the gaps" thus explains how the brain can be "fooled" by the illusionist or magician in much the same way as it is fooled by an optical illusion. This also explains how sleight of hand and misdirection aid the magician in their art - we see what we expect to see, and what we do not see (but expect) we fill in from memory. So in reality the "magic" is in our brain, and is a part of how we normally interact with the world - which raises a further question of whether "perception" is in fact "reality?" But that's a question and an issue for later... much later.
Until next time, accept no substitutes and ask for the genuine Lab Rats - at The Lab Rats' Guide to the Brain!