Activity #11

I quoted a passage from Feder (1999) that describes a card trick that can be used to teach students about hypothesis development and testing. In particular, the trick can help to teach students that it is not justifiable to accept a hypothesis simply because one has tested and rejected other hypotheses. Tim Gaines responded by briefly describing a variation on this trick.

Mon, 4 June 2001
Jeffry P. Ricker
Scottsdale Community College
jeff.ricker@sccmail.maricopa.edu

Feder (1999) described a card trick that he uses as a classroom demonstration. The purpose of the trick is to teach students about hypothesis development and testing. Feder was most concerned with teaching students that one cannot accept a hypothesis (especially if it is an untestable, as many paranormal and pseudoscientific hypotheses seem to be) simply because one has tested and eliminated all other testable hypotheses one has thought of. Although Feder didn't describe every detail of the trick, these details (or your own variations) are very easy to figure out on your own.

Reference: Feder, K. L. (1999). Frauds, myths, and mysteries: Science and pseudoscience in archaeology (3rd ed.). Mountain View, CA: Mayfield.

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[Beginning of quoted material from pp. 29-30)

Let me explain a card trick I perform with Dr. Michael Park--a friend and colleague--to show why this process of elimination doesn't work. I ask a student in class to select a card from a deck, showing the face of the card to me and all the other students in the room while my colleague sits comfortably in his home office twenty miles away. From the classroom, I then call Mike on the phone and "telepathically" transmit the face of the card across the telephone wires. We can get it right every time; our years of collaborative work have left us incredibly tuned-in to each other psychically. Or so we would have our audience believe.

Are you a skeptic? If so, you might ask:

1. Is it a fixed or gimmicked deck?
2. Is there a hidden mini-camera or microphone in the classroom with a feed to Mike's house?
3. Is the student who selects the card a plant, a co-conspirator in the magic trick?

All good questions, but the answer is "no" each time. Based on your three incorrect suggestions, would it make sense to conclude that what you saw was not a trick at all but an example of real "supernatural magic" or telepathy? Wouldn't it make more sense simply to admit that you do not have the expertise to come up with a more reasonable hypothesis? ....

[The trick] is actually quite simple. When I call Mike on the phone, in the seemingly innocuous chatter that transpires between us as he attempts to "read my mind," I simply tell him which card it is. "But," you object, "don't students pick up on this?" No, they don't, because our conversation is in a simple, but pretty much impenetrable, predetermined code.

It works like this. When I call, I address Mike using the code we both know. If I say "Hello Mike," that indicates that it's a red card, but if I say "Hi Michael," it's a black card. Suppose I say "Hi Michael" (indicating the card is black), and next I say "Are you ready?" In our code that means it's a club, but if instead I say "We are ready here," it's a spade. [Of course, if Feder had indicated that it was a red card by saying, "Hello Mike," then the same two phrases--"Are you ready?" or "We are ready here"--could have indicated a heart or a diamond, respectively.] Everything else I say is based on the code and identifies the card to my accomplice: picture card versus number, even the actual value of the card [although Feder doesn't say it, I imagine the best way of doing this would be to have the accomplice count up the deck until he/she reaches the correct card, at which time the accomplice could be stopped by saying something like, "OK"]. The key to the code is that everything I say is something that would be expected in our conversation; it all sounds like reasonable, ordinary, harmless banter wholly unrelated to his "psychically reading" the card. Mike doesn't even need to memorize the code--he can have it written down on a piece of paper.

[End of quote]
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Tue, 5 Jun 2001
Tim Gaines
Presbyterian College
mtgaines@mail.presby.edu

I have heard of an impressive variation of this demo. A randomly selected student in the class calls a number and asks for the friend of the prof. After the student explains what is going on, the friend on the other end of the line names the card. The student is actually inadvertantly telling the friend what the card is by asking for him by NAME. I don't remember the name code, but it is something like: male for black cards and female for reds, one syllable for face cards and two for numbered, etc. I may be able to find the code if there is interest, but anyone could make up one of their own.