How do magic tricks work in the mind? To answer this, we first had to study the tools used by magicians: playing cards.
Specifically, we measured five factors of cards that may be relevant to magic tricks:
- visibility, how well a card is detected among other cards;
- memorability, how well it is remembered;
- likability, how much it is liked;
- verbal accessibility, how likely it is chosen when asked to name a card; and
- visual accessibility, how likely it is chosen when asked to visualise a card.
Visibility: How well can people detect particular cards?
We showed 96 people a fast series of playing cards while they tried to detect a particular card in the series.
People detected simpler and distinct cards better. They detected the Ace of Spades better than other Aces, and Aces better than number cards.
Suit had no effect on how well people detected cards. However, within number cards, people seemed more likely to declare Spades absent.
People also seemed particularly likely to report seeing the Six of Hearts and Six of Diamonds, whether or not they appeared.
Memorability: How well can people remember particular cards?
We showed the same 96 people a slow series of cards, then they tried to remember whether a particular card appeared in the series.
Similar to the visibility study, people remembered the Ace of Spades better than other Aces, and Aces better than number cards.
People could remember different number cards equally well, but seemed more likely to declare the card absent as the number increased.
Likability: How much do people like particular cards?
We showed 48 people two cards side-by-side and asked which one they liked more.
People showed strong preferences for particular cards. They preferred the Ace of Spades over other Aces on average, Aces over number cards, and face cards over number cards.
They usually seemed to prefer Spades and Hearts more than Clubs and Diamonds.
Women seemed to prefer lower-valued cards (Twos and Threes) more than men did.
Verbal accessibility: Which cards do people verbally choose the most?
In a separate experiment, we asked 667 people to name a playing card.
We saw the same pattern of results as in the Likability study. People chose the Ace of Spades more than other Aces, and Aces and face cards more than number cards.
More than half of the people chose one of four cards: the Ace of Spades, Queen of Hearts, Ace of Hearts, and King of Hearts.
For number cards, people seemed to name Threes and Sevens the most.
Women seemed more likely to name the King of Hearts, and men the Queen of Hearts.
People rarely chose middle-valued number cards. Of 423 valid responses, nobody chose the Four of Spades, Five of Clubs, Five of Diamonds, Six of Clubs, or Six of Diamonds.
Many people misunderstood the question. Some people named card games, and a few literally named a card ("Joe").
Visual accessibility: Which cards do people visually choose the most?
In another experiment, we asked 700 people to visualise a playing card, then tell us what it is.
We saw the same pattern of results as in the Verbal Accessibility study.
However, people seemed more likely to choose the Ace of Hearts when asked to visualise one rather than name one.
People chose every card except the Five of Spades.
Some people mentioned different kinds of cards ("business card"), others told us what a playing card is ("cardstock laminated with plastic").
Relationships between factors
We also looked at whether any of these five factors related to each other. Some of them did.
People would more likely misreport remembering accessible cards. When asked, in the Memorability study, whether they remembered a card, people would often misreport seeing accessible cards like the Ace of Spades or Queen of Hearts.
People also liked, verbally chose, and visually chose the same kinds of cards.
The next step is to apply this knowledge of cards to magic tricks, to better understand how magic works in the mind.