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        riddles >> what happened >> Mind Reader
        
(Message started by: Locke64 on Jan 12th, 2007, 4:57pm)
Title: Mind Reader
Post by Locke64 on Jan 12th, 2007, 4:57pm
Check out this flash mind reader (http://www.albinoblacksheep.com/flash/mind.php).

Can you explain how it does it?



PS: I can, I'm just wondering if you can. ;)
Title: Re: Mind Reader
Post by Whiskey Tango Foxtrot on Jan 12th, 2007, 5:50pm
I didn't look at the one you posted but they all operate on the same principle.  [hide]For example, 44 and 45 both return the same number, 36.  Or 20 through 28 all return 18.  It's not really that much of a trick.[/hide]
Title: Re: Mind Reader
Post by towr on Jan 14th, 2007, 7:30am
00 is a two digit number, isn't it? :P
Title: Re: Mind Reader
Post by Locke64 on Jan 14th, 2007, 10:49am

on 01/14/07 at 07:30:20, towr wrote:
00 is a two digit number, isn't it? :P

...


Since no one posted it yet, and it is very easy, I'll post it.

[hideb]Any 2-digit number can be represented by 10x+y.  First, you add x+y, then you subtract from the original number, thus giving you this equation:
10x+y-(x+y)
distribute the negative,
10x+y-x-y
'y's cancel out, and subtract one x from 10,
and you get 9x.  Therefore, the answer is always a multiple of nine.  Notice that all multiples of nine have the same symbol.[/hideb]
Title: Re: Mind Reader
Post by towr on Jan 14th, 2007, 10:59am

on 01/14/07 at 10:49:23, Locke64 wrote:
[hide]Notice that all multiples of nine have the same symbol.[/hide]
Except [hide]0, 90, 99[/hide].
Title: Re: Mind Reader
Post by Locke64 on Jan 14th, 2007, 11:06am

on 01/14/07 at 10:59:26, towr wrote:
Except [hide]0, 90, 99[/hide].

Yeah, because [hide]in order to get 0, x would have to be zero, and in order to get 90 or 99, x would have to be 10 or 11.  It must be a 2-digit number.[/hide]
Title: Re: Mind Reader
Post by JP05 on Jan 14th, 2007, 11:16am
I remember this to be the same thing but with a nicer animation. Seems that towr proved it too.

http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_easy;action=display;num=1151194235;start=0#0
Title: Re: Mind Reader
Post by Icarus on Jan 14th, 2007, 7:20pm
If you were to search enough, I think you would find at least 2 more versions of this same trick that people have posted - plus several other tricks that also rely on the fact that a number and the sum of its digits are equivalent modulo 9. In fact, almost all of the math tricks I have heard rely on this fact.
Title: Re: Mind Reader
Post by towr on Jan 15th, 2007, 1:19am

on 01/14/07 at 19:20:32, Icarus wrote:
In fact, almost all of the math tricks I have heard rely on this fact.
There's a few relying on odd/even; and of course binary coding.
Title: Re: Mind Reader
Post by Sir Col on Jan 16th, 2007, 12:17am
I can't remember if this classic version has been posted here before, but I added this one to my website some time ago:
http://mathschallenge.net/index.php?section=rec&ref=experiment_2

It's one of my favourites because the "trick" here is not at all obvious.


This one is a little easier to figure out:
http://mathschallenge.net/index.php?section=rec&ref=experiment_3
Title: Re: Mind Reader
Post by Icarus on Jan 16th, 2007, 2:21pm
That's why I said that only almost all the math tricks I've heard depend on it. Even Sir Col's second example does: The rearranged digits of the number has the same digit sum, so the two numbers are = mod 9. Therefore, their difference = 0 mod 9. Hence its digits add up to a multiple of 9. Once you drop a digit, this is no longer so. So add up the digits of the final answer, and subtract that from the next higher multiple of 9. The result is the digit that was dropped.

The first challenge is more creative. Of course, you have to go to H for it to work - stopping at G would be ambiguous!
Title: Re: Mind Reader
Post by tiber13 on Mar 12th, 2007, 5:48pm
i chose 99 but it came out with a snowflake, not a bell!
Title: Re: Mind Reader
Post by tiber13 on Mar 12th, 2007, 5:49pm
i tried 10 times but it was always wrong ???
Title: Re: Mind Reader
Post by Icarus on Mar 12th, 2007, 7:27pm
You have to follow the instructions for it to work: Note that it says you should pick a two digit number then subtract the sum of the digits of the number from itself. It is the result of this practice that gives you your symbol.

For example, if you originally pick 99, you have to calculate 99 - (9+9) = 81. It is the symbol for 81 that will appear, not the symbol for 99.
Title: Re: Mind Reader
Post by Iceberg on Mar 31st, 2007, 12:41am
Forget math tricks and multiples. A lot of the symbols were the same even right next to each other
Title: Re: Mind Reader
Post by BNC on Mar 31st, 2007, 3:21pm

on 03/31/07 at 00:41:49, Iceberg wrote:
Forget math tricks and multiples. A lot of the symbols were the same even right next to each other

However, without the "math tricks and multiples" it wouldn't have worked every single time.
Title: Re: Mind Reader
Post by ThudanBlunder on Mar 31st, 2007, 6:02pm

on 01/12/07 at 16:57:22, Locke64 wrote:
Check out this flash mind reader (http://www.albinoblacksheep.com/flash/mind.php).

Here's (http://sprott.physics.wisc.edu/pickover/esp.html) another you might like.
And how about this (http://intelligence.sergi5.com/)?
Title: Re: Mind Reader
Post by Icarus on Apr 1st, 2007, 12:31pm
Gosh - that first site is really amazing! It's even better than it claims. Try this: [hide]don't just call out one card. Call them all out. It'll still work! Every card you called will be removed from the 2nd page![/hide] WOW! :o:o

What is a real hoot are the people who wrote in to claim that it failed to work for them - particularly those who claim it failed repeatedly!  ::)



The second site is more interesting, in my opinion, as it is a real accomplishment, not just a trick. Even if the accomplishment is just a nice pattern recognition routine.
Title: Re: Mind Reader
Post by ima1trkpny on May 13th, 2007, 12:52pm
I didnt get quite the same result from the first site... I worked twice and failed 5 times when calling out multiple cards... very neat experiment though... i wonder how that one works... anyone?
Title: Re: Mind Reader
Post by william11141 on May 13th, 2007, 3:15pm
OMG lol, pretty eazy if you think about it... when you choose any 2 digit number and do the magic-subtraction-doohicy thing you get surtain numbers. The graph thing changes everytime...but if you look closely, the symbols for all the possable finished answers are the same, and thats the symbol that apperas on the ball... :P
 ops, locker already gave the answer... DAMMIT! i didnt get here fast enogh... >:(
Title: Re: Mind Reader
Post by Icarus on May 13th, 2007, 6:29pm

on 05/13/07 at 12:52:08, ima1trkpny wrote:
I didnt get quite the same result from the first site... I worked twice and failed 5 times when calling out multiple cards... very neat experiment though... i wonder how that one works... anyone?


You need to keep better track, then. NONE of the cards on the first page are on the second page! So it doesn't matter what you pick, you won't see it on the second page. The trick works because people only keep track of their picked card, they don't pay any attention to the other cards.

This is why I thought it was a hoot that people kept writing in to him to say it didn't work for them!
Title: Re: Mind Reader
Post by ima1trkpny on May 16th, 2007, 9:45pm
Thanks Icarus... I didn't notice that >.<
Title: Re: Mind Reader
Post by Aurora on May 28th, 2007, 8:22am
Icarus, you are a genius, I had come across that  site before and had no idea of what was going on, (although I wasn't inclined to believe that the software tracks your eye movement or where your mouse is on the page).

It's so simple yet incredibly effective. I just want to know how long it toook you to figure it out!
Title: Re: Mind Reader
Post by ima1trkpny on May 28th, 2007, 8:42pm
I second that! I only noticed that the same number of cards were there so I couldn't figure out what was going wrong... seriously... how long did it take you? (probably not long  :-/ )
Title: Re: Mind Reader
Post by towr on May 28th, 2007, 11:31pm
I don't know about Icarus, but usually the second thing I try is cheat; in this case, take two cards. And hey, neither is there the next time.
Trying to cheat at a game is the fastest way to understand the rules, because you have to find their limits to break them.
Title: Re: Mind Reader
Post by Grimbal on May 29th, 2007, 2:48am
Or by pure logic.

Without knowing your choice, it knows your card isn't visible any more.  Either it is luck (unlikely) or it is true whatever your choice.  That means none of the initial cards can be seen any more.
Title: Re: Mind Reader
Post by towr on May 29th, 2007, 5:21am

on 05/29/07 at 02:48:54, Grimbal wrote:
Or by pure logic.

Without knowing your choice, it knows your card isn't visible any more.  Either it is luck (unlikely) or it is true whatever your choice.  That means none of the initial cards can be seen any more.
That's dismissing the unlikely, but logically possible, option that it really does read your mind (or something of the sort). So while you can deduce that, if it doesn't read your mind and it's not pure luck then it must change all cards, you'd still have to check the conclusion.
Title: Re: Mind Reader
Post by Grimbal on May 29th, 2007, 6:56am
That's a possibility I dismissed immediately. :P

I used the following assumptions:
Assumption 1: a computer doesn't read minds
Assumption 2: the program doesn't rely on pure luck.
From there we can deduce the trick.

OK, maybe it does not prove the case, but it strongly hints at it.  You are right that you should check the conclusion.  Anyway, I can't imagine someone who understands the trick and does not play another game to check it.

And yes, a program could use subliminal clues to force a choice.  It is not reading your mind but still somehow knowing your supposedly secret  thoughts.

Last, a program could rely on pure luck.  The kind of program that gives you tomorrow's horse race winner and asks for payment only if it is correct.
Title: Re: Mind Reader
Post by towr on May 29th, 2007, 7:37am

on 05/29/07 at 06:56:58, Grimbal wrote:
Last, a program could rely on pure luck.  The kind of program that gives you tomorrow's horse race winner and asks for payment only if it is correct.
If you give say 5 freebies, one in 32 people should get a straight run of wins, and so they'd be likely to think it's always right. Then you charge for further predictions.
I've heard it works well as a scam.
Title: Re: Mind Reader
Post by Icarus on Jun 3rd, 2007, 1:58pm

on 05/28/07 at 23:31:41, towr wrote:
I don't know about Icarus, but usually the second thing I try is cheat; in this case, take two cards. And hey, neither is there the next time.
Trying to cheat at a game is the fastest way to understand the rules, because you have to find their limits to break them.


Pretty much the same, except in this case, I didn't bother to wait for the second try. I just noted all the cards in the original picture, clicked, and compared. I did try it again - which is how I noted that the guy was so lazy as to use the same two gifs every time instead of switching the cards out. I also viewed the source out of curiosity. He put in a bunch of psuedocode to try to fool hackers, but anyone with even modest programming knowledge should be able to tell it's commented out, and wouldn't be executable even if it weren't.


on 05/29/07 at 06:56:58, Grimbal wrote:
That's a possibility I dismissed immediately. :P

I used the following assumptions:
Assumption 1: a computer doesn't read minds
Assumption 2: the program doesn't rely on pure luck.
From there we can deduce the trick.

OK, maybe it does not prove the case, but it strongly hints at it.  You are right that you should check the conclusion.  Anyway, I can't imagine someone who understands the trick and does not play another game to check it.

And yes, a program could use subliminal clues to force a choice.  It is not reading your mind but still somehow knowing your supposedly secret  thoughts.

Last, a program could rely on pure luck.  The kind of program that gives you tomorrow's horse race winner and asks for payment only if it is correct.


This kind of like evaluating all those perpetual motion, heat flow reversing, concepts (for example, the log motor). You know for a fact that something is wrong with the physics behind them simply because they violate the 2nd law of thermodynamics. But this really doesn't explain what the flaw is. The fun in such puzzles is figuring out what trick they use to make the impossible seem plausible.

Similarly here: yes, it was obvious the claim was false, but "how does the trick work" was the interesting question.
Title: Re: Mind Reader
Post by BNC on Jun 4th, 2007, 2:40am

on 06/03/07 at 13:58:42, Icarus wrote:
Pretty much the same, except in this case, I didn't bother to wait for the second try. I just noted all the cards in the original picture, clicked, and compared.


But don't you see -- it only means it works better! Pick one card, and only that card will go. Pick two -- both (and only both) will disappear. Even if you pick all five, they will go.
Unlike human ESP that will only work on lousy one card, the PC can handle many cards! it works better!

I, for one, welcome our new PC overlord.
Title: Re: Mind Reader
Post by Icarus on Jun 4th, 2007, 4:54pm

on 04/01/07 at 12:31:22, Icarus wrote:
Gosh - that first site is really amazing! It's even better than it claims. Try this: don't just call out one card. Call them all out. It'll still work! Every card you called will be removed from the 2nd page! WOW! :o:o


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