

Andy Moss Special user 704 Posts 
The 'Monty Hall Paradox' is a fine one but perhaps not easily incorporated iinto a solid magical effect since the odds are only 66.66% in our favour after all.
I recently came across 'The two doors to freedom paradox'. This works for us 100% of the time and may be more user friendly for us. One idea is to use three half walnut shells and three small marbles. Two of the marbles are white and the third is black. The three walnut shells represent three caves in which live two benevolent elves who will feed you and give you shelter and one malicious ogre who will kill you and eat you if he can. The ogre is represented by the black marble and the elves by the white marbles. The spectator may place the ogre under any one of the three shells and place the remaining white marbles under the other two whilst your back is turned. You state that the elves because they are pure in spirit will always speak the truth to any question that is addressed to them. In contrast the ogre is by nature deceitful and may either lie or answer truthfully as he so chooses in order to best deceive. Then the fun begins! You may address any one of the caves by pointing at it and the spectator is then obliged to take on the respective role of either the elf or the ogre depending upon the inhabitant/colour of marble that only they know lies hidden within this cave. You can then address each cave in any order (it does not matter) asking the following question. "Am I safe to enter this cave?" You simply have to remember to focus your attention on the two caves that do not contain the unknown inhabitant who is currently addressing you. If you receive a positive answer on the first of these two remaining caves then this cave certainly contains an elf. If you receive a negative answer then switch to the other cave of the two. This will likewise always contain an elf. This presentation can be presented as if you have a one in three chance of being eaten by the ogre. The specctator will believe this to be logically the case. However you may repeat this endlessly until they are baffled by your perfect luck/intuition! Enjoy. Andy. 
MC Mirak New user 28 Posts 
Florida by Phill Smith is an interesting take on the hidden 66% odds in our favor kind of approach. Similar to Doug Dyment's Penney's from Heaven, these kinds of approaches benefit from being repeated.
I prefer these mathematical odds types effects more than logic puzzles because, when I've asked people, that is exactly what they think happened, a logic puzzle. The one exception I've found to this is Tequila Hustler (I use the truthlie followup) so maybe it's just me now that I think about it... Thanks for sharing the above, was just thinking out loud. 
Andy Moss Special user 704 Posts 
You're welcome.Yes,the above effect should be presented in such a way that it does not seem like a logic puzzle.
For example we might keep things as simple as possible and dispense completely with the story presentation. Simply phrase the question as "Is the black marble under this shell?" The spectator answers yes or no. Remember in their mind the spectator will be thinking down the following route of false logic... 1) There is no way that the mentalist can know for certain if I am telling the truth or not when I answer. The mentalist is not psychic. 2) This is logically the case since there is no way that the mentalist saw which shell I put the black marble under.I also got to mix up all the walnut shells as well. Therefore there was utter randomness in the set up. 3) There is certainly a one in three chance that the mentalist is going to fail since there are three shells and one loser marble. 4) Therefore I will try my best to confuse and misled the mentalist when I have the opportunity to do so by changing the tone of my voice or perhaps I will adopt a poker face throughout." So since the above is true in the spectator's mind it is best to present this as a psychological test whereby you are reading the spectator's body language and listening to their voice for clues. What I like about this particular three variable effect is that things are kept so pure and simple. The order of the selection of the shells each time can also be made to seem completely random with no methodology discernable. 
Pit Boss Special user 538 Posts 
Very interesting. I'm sure it's just me, but I'm not following the 3 questions and how that tips the info to you. Could you elaborate a bit?
Thanks, JD 
ddyment Inner circle Gibsons, BC, Canada 2167 Posts 
It's explained in the OP, but not very clearly. Asking the questions is a twostep process: first, you point to one of the shells (this is what directs the participant to either tell the truth or optionally lie (because only the participant knows the nature of the creature hiding beneath that particular shell)); second, you ask the question(s).
If you're still lost, look up a description of the "two doors to freedom" problem. Here is a good one. Andy has cleverly enhanced the original by (apparently) giving it another layer.
Doug Dyment's Deceptionary :: Elegant, Literate, Contemporary Mentalism ... and More

Andy Moss Special user 704 Posts 
Thank you Doug for offering everyone the link to the paradox. This web page is the relevant one and the one that inspired my own take.

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