Magicians are in the business of testing the limits and nature of human perception. It's no surprise, then, that today's cognitive scientists are uncovering features of the mind that magicians have understood (and exploited) for hundreds of years. A close look at some of the many books on conjuring published since the 16th century reveals insights that are only now making their way into the scientific literature.
1. Don’t Look Now, But...
Sleight-of-hand artists have long used subtle eye movements to manipulate the attention of their audiences. In their 1909 book The Art of Magic, T. Nelson Downs and John Northern Hilliard wrote that “it is scarcely necessary to say,” that while performing a secret maneuver, “[t]he eyes of the performer ... must never for an instant glance at the right hand” as it executes the sleight. “Should the performer forget himself in this respect,” they caution, “the audience will instantly suspect” a move has occurred.
In recent years, the effect of "gaze perception" on everything from attention to social cognition has become a rich area of psychological research. Not surprisingly, magic has proven a useful experimental tool. In their 2009 article in the journal Visual Cognition [PDF], for instance, researchers at the University of Durham measured how a magician’s gaze influenced the attention of 32 spectators during a trick. Sure enough, the authors found that “participants spent less time looking at the critical hand when the magician’s gaze was used to misdirect their attention away from the hand.” Downs and Hilliard had scooped them by a century.
2. What’s the Difference?
Yet another topic to catch fire among cognitive scientists in the last two decades is so-called “change blindness,” or, as researchers Daniel Simons and Ronald Rensink have described it, “the striking failure to see large changes that normally would be noticed easily.” In one representative experiment, a researcher stops pedestrians on a college campus to ask for directions. This exchange is briefly interrupted by two individuals carrying a large door, during which time the original researcher is replaced by a different person entirely. In more than half the cases, the pedestrians giving directions didn’t notice when their interlocutor completely transformed into a new person.
Of course, magicians got there first. In the domain of card magic, for example, many methods rely on minor visual discrepancies that, even to a close observer, are all but invisible. Some effects require two similar-looking cards—the eight of spades and eight of clubs, say—to be swapped, often quite brazenly. Perhaps the earliest published mention of this specific principle appeared in August Roterberg’s 1897 book New Era Card Tricks.
3. Pick a Side Dish, Any Side Dish
Methods for simulating free choice are among the oldest tools available to magicians. Just consider the countless techniques for “forcing” a card while maintaining the appearance of free selection from the deck. The idea existed at least as far back as 1584, when Reginald Scot published The discoverie of witchcraft, the earliest known English-language book to provide detailed descriptions of conjuring tricks.
And yet, the insight that irrelevant, invisible factors can influence our decisions in predictable and unnoticed ways is just now getting its due in the academic world, most notably among practitioners of behavioral economics. The field has produced a steady stream of bestselling books, and earned one of its forefathers, Daniel Kahneman, the 2002 Nobel Memorial Prize in Economic Sciences. It’s also become a favorite of policy experts like Cass Sunstein, who has argued vigorously for using insights from behavioral economics to secretly “nudge” citizens towards certain decisions, whether saving for retirement or choosing healthier foods.
4. Where Were You the Night the Elephant Disappeared?
Imperfect memories can be a conjurer’s best friend. For audiences, magic performances often seem more impressive—and impossible—in retrospect. As one writer notes in a 1918 issue of the British magic publication the Magic Circular, it is to an audience’s “lapse of memory that we owe half of the wondrous accounts of things that never happen but which enhance our reputation nevertheless.” Indeed, some performers are skilled at encouraging exaggerated memories in ways I’m not at liberty to discuss here.
Our tendency to create less-than-accurate memories after the fact—what psychologists sometimes call “reconstructive memory”—has been gaining much notice lately, particularly with regards to its effects on eyewitness testimony in the American legal system. Psychologist Elizabeth Loftus has found, for instance, that the questions “asked immediately after an event can introduce new—and not necessarily correct—information which is then added” to a witness’ memory [PDF].
5. The Audience is Always Right—Unfortunately
Cognitive shortcomings don’t always work to a magician’s advantage. As working performers know all too well, it’s not uncommon for an audience member to interrupt a trick by shouting out an incorrect explanation for the effect being performed (“it’s up your sleeve!” and “magnets!” are perennial favorites). Even when such ill-considered assertions explain nothing at all (how could a magnet be involved in a coin vanish?), it’s sometimes enough to leave audiences unimpressed.
Such episodes serve as textbook examples of what psychologists Frank Keil and Leonid Rozenblit have named the “illusion of explanatory depth,” or the feeling that we “understand complex phenomena with far greater precision, coherence, and depth than [we] really do.” As they write in a 2002 paper in the journal Cognitive Science [PDF], “laypeople ... usually remain unaware of the incompleteness of their theories,” in part because they “rarely have to offer full explanations for most of the phenomena that they think they understand.” I still say it was magnets.