A card trick is one of the most common magic tricks known to humankind. Typically, when a magician is doing a card trick, he would ask his subject to pick any card from his deck. If that person chooses the three of diamonds, he might be "primed" by the magician to pick that card without his knowledge.

According to the recent paper published in the Proceedings of the National Academy of Sciences (PNAS), that may be caused by certain subtle gestures and verbal cues that can unconsciously influence the decision-making.

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Visual priming

The National Library of Medicine website of the National Center for Biotechnology Information defines visual priming as the phenomenon when the classification response is faster to a stimulus that looks identical to a previous stimulus than a stimulus only similar by name.

A famous experiment in 1957 about visual priming involving subliminal advertising was conducted by a market researcher named James McDonald Vicary. The study included 45,000 people attending screenings of the movie Picnic at Fort Lee, New Jersey.

The theater was repeatedly shown brief advertisements for food and beverages such as "Drink Coca-Cola," or "Hungry? Eat popcorn" that lasts 1/3,000th of a second during the film. Vicary reported an 18.1 percent increase in sales in Coca-Cola and a surprisingly 57.8 percent increase in popcorn sales due to the ad.

The success of the was featured in a 1973 episode of Columbo, prompting the CIA to issue a cautionary report.

However, there is one problem: Vicary was a fraud. No one has ever replicated his results, not even him. He later confessed that he falsified his findings and that the story was just his gimmick to save his struggling marketing business.

But studies on visual priming did not stop there. Nowadays, there have been numerous legit experiments about it but with certain limitations. For example, one test would only allow the subjects to choose from two to three choices, done in a tightly controlled laboratory setting.

There is a substantial anecdote that the methods used by magicians in doing their card tricks are effective; it just had not been scientifically studied. These subtle techniques that involve visual priming are incorporated in their performances.

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Using Priming Techniques in Doing Card Tricks

Psychologist Alice Pailhès of Goldsmiths University of London and co-author of the PNAS paper said she is confident in using techniques by the magicians in her study on how unconscious factors can influence decision-making.

Pailhès said he is inspired by British illusionist Derren Brown that uses mental priming and forcing techniques that involves visual and verbal cues in his performances. He leads his subject into thinking of picking the three of diamonds card- an unlikely card for people to choose for a 52-card deck.

Magic or Science? The Secret of Card Tricks Finally Revealed
(Photo : Pixabay)
Magic or Science? The Secret of Card Tricks Finally Revealed


Brown would first ask his audience to "mentally transmit" a card by picking one, which is bright and vivid. This would prompt the audience to think of a red-suited card. Then Brown would ask the audience to imagine a screen while subtly making hand gestures that would form a diamond shape to prime the audience to think of diamonds.

To prime his audience into thinking the number "3," he would ask them to imagine the "little numbers down in the corner of the card and in the top." He rapidly draws the number three in the air, as if he is writing them on an imaginary card with his index finger.

Finally, he would ask his audience to imagine "things in the middle of the card, the boom, boom, boom, the suits," while pointing to three imaginary symbols in the air. Unknowingly, the audience has been primed to think of the three diamonds card.

The priming only lasts for 15 seconds.

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