The Conjurer, by Hieronymus Bosch, depicts a medieval magician performing for a small crowd, while pickpockets steal the spectators' belongings. The painting, on display at the Musée Municipal in St.-Germain-en-Laye, France, illustrates that magicians have long known how to hack into our mental processes. The principles of magic, refined and perfected over the centuries, provide neuroscientists with new ways to study the brain and could help them in their quest to reveal how the organ performs the greatest trick of all - consciousness itself.

"In principle, neuroscience and magic have little in common," says Susana Martinez-Conde, director of the Visual Neuroscience Laboratory at the Barrow Neurological Institute in Phoenix, Arizona. "In fact, they are hugely complementary and magicians have a lot to offer us. They can manipulate the attention and consciousness of spectators so much better than we do in the lab." A few years ago, Martinez-Conde and her husband Stephen Macknik decided to investigate exactly how magicians fool the brain so adeptly. In doing so, they founded the exciting new discipline they refer to as 'neuromagic,' which aims to "pop the hood on your brain as you are suckered in by sleights of hand."



"It all started when Stephen and I were asked to co-chair the

11th annual meeting of the Association for the Scientific Study of Consciousness," Martinez-Conde explains. "Traditionally, this was a very academic conference that had no impact outside the specialist field. We wanted to reach the general public as well, but we weren't sure exactly what to do."

The wife-and-husband team went to Las Vegas, where the conference was to be held. It was then, while scouting for potential conference venues, that the idea first came to them. "We saw a lot of ads for magic shows and realized that was the connection we were looking for. We contacted a number of magicians, such as Penn and Teller, James Randi and Apollo Robbins and invited them to a special symposium [at the conference], to share their insights into what makes magic work in the mind of the spectator."

Illusions on top of illusions

Magicians have a repertoire of perhaps several dozen techniques which they use to deceive spectators and enhance perception of their tricks. One of these is 'misdirection,' which exploits inattentional blindness and change blindness, two phenomena that psychologists have studied intensively in recent years.

Studies of inattentional blindness show that focused attention can make us oblivious to sights that would otherwise be glaringly obvious, while studies of change blindness show that dramatic changes in a scene can go unnoticed if they occur during a brief interruption, even when we look directly at the scene.

Magicians take advantage of this to manipulate their spectators' attentional spotlight. They know, for example, that the eyes give off important social cues, and that people have a natural impulse to pay attention to the objects that others are attending to. They exploit this 'joint attention' by using their eye movements to divert the audience's attention away from the 'method' – the secret action behind the trick – and towards the magical effect.

They also know that the sudden appearance of a new and unusual object will immediately draw the audience's attention. Hence, producing a flying dove gives them an opportunity to perform other hidden manoeuvres.

These cognitive illusions are used together with optical illusions that exploit the properties of light; visual illusions that exploit how the brain interprets images; memory illusions that exploit the reconstructive nature of our recollections; special effects such as explosions; and various gimmicks, including secret devices and mechanical artifacts. (Both Martinez-Conde and Macknik have studied visual illusions extensively, and about 10 years ago they set up the hugely popular Best Illusion of the Year Contest.)

"Instead of isolating the specific variables and using one effect, magicians lump everything together, putting illusions on top of illusions," says Martinez-Conde. The magic show is a form of 'mental jujitsu' that bombards the senses, overloading the brain with multiple tasks that cannot be processed simultaneously. "It's a super-stimulus and we really are defenceless. It's virtually impossible for spectators to penetrate these layers and get at the method of the trick."

For my next trick...

For their latest study, the neuromagicians collaborated with professional magician Mac King to investigate a trick called the coin vanish. First, they filmed him performing real and simulated coin tosses. As the film clip shows, he tosses a coin vertically with his right hand, then pretends to toss it from his right to his left hand, but secretly holds it in his right hand. A split second later, he closes his left hand, as if to catch the coin, then opens his left hand to show that it has magically disappeared.

Magicians often direct their gaze at the presumed position of the coin while performing this trick. Thus, they will look first at their right hand and then shift their gaze to the left, without looking directly at the audience. The researchers wondered if joint attention enhances perception of the trick, and if Mac King might further enhance the illlusion by looking at the audience whilst performing the simulated coin toss. They showed various versions of the film clip to their participants and used a high-speed video camera to record their eye movements.

In the first experiment, nine participants watched a shortened version of clips showing Mac King performing real and simulated coin tosses, which ended before he opens his left to reveal that the coin has vanished. Each participant was shown clips of 50 real and 50 simulated coin tosses, presented randomly, and asked to press a button when they saw the coin flying between his hands.

The participants perceived more than nine out of ten of the real coin tosses across all 50 trials. In the simulated coin toss condition, they perceived about three quarters of the first 10 trials, but this dropped significantly to about half during the remaining 40 trials, showing that they quickly learned to discrimiate between the real and illusory coin tosses. Magicians sometimes say that they should never perform the same trick twice, but these results show that the coin vanish trick is resistant to repeated viewing.

The second experiment was almost exactly the same, except that six different participants were shown slightly longer clips that included the 'reveal' at the end. Again, the participants saw nine out of ten of the real coin tosses, and about six of the first ten simulated tosses. This time, however, they only perceived about one fifth of the simulated tosses in the remaing 40 trials, showing that the 'reveal' at the end of the clips significantly improved their ability to discriminate between the two after the initial ten trials.

In the third and final experiment, eight more participants were shown the same clips as those used in experiment two, as well as three additional clips showing Mac King performing multiple real and simulated coin tosses. This experiment was carried out under three different conditions. In half of the trials, the magician's head was hidden from view by a black rectangle, so that the participants could not see his gaze direction. In some conditions, the participants were asked to fix their gaze on a red cross that appeared on his face (or the equivalent position in trials where it was obscured). In others, they were allowed to let their gaze wander freely, as it would during normal viewing of a magic show.

Surprisingly, the illusion was stronger when the magician's face was blocked: the participants reported seeing seven out of ten real coin tosses when they could see his face and nine out of ten when they couldn't. Analysis of their gaze dynamics showed that the participants avoided looking at the magician's face in all the experiments, doing so only at the very end of the trick.

These findings conflict with previous work showing that a magician's gaze misdirection intensifies spectators' perception of illusions. The effects of gaze direction on the perception of magic may differ from one trick to another, and can probably enhance, lessen or leave unchanged its perception, depending on which trick is being performed.

The researchers suggest that the magician's level of expertise may be a key factor in how gaze direction affects perception of the coin toss illusion. The film clips used in the study indicated that Mac King's timing during the trick is impeccable - the timing of his simulated coin tosses differed from that of his real ones by about 35 thousandths of a second. Such accuracy could, therefore, make misdirection unnecessary for master magicians performing this particular trick.

The collaborations between Martinez-Conde, Macknik and the magicians have already been very fruitful, and so far have produced numerous academic papers, as well as a successful popular science book called Sleights of Mind, published this time last year. Martinez-Conde believes that this is just the tip of the iceberg, though.

"This is a long-term project and we have a number of ongoing collaborations with magicians not only in the U.S. but internationally," she says. "We're now pursuing their intuitive knowledge about the connection between attention and emotions, which is not understood at all in the cognitive sciences. I expect we'll be publishing regularly on magic and neuroscience."

References: Cui, J., et al. (2011). Social misdirection fails to enhance a magic illusion. Front. Human Neurosci., DOI: 10.3389/fnhum.2011.00103

Macknik, S., et al. (2008). Attention and awareness in stage magic: turning tricks into research. Nat. Rev. Neurosci., DOI: 10.1038/nrn2473

Macknik, S., Martinez-Conde, S. & Blakeslee, S. Sleights of Mind: What the neuroscience of magic reveals about our everyday deceptions. New York: Henry Holt, 2010.