This is part 2 of the "Neuroscience of Magic/Illusion" series, and will deal with the second great trick of magicians and illusionists: misdirection. Misdirection is common to magic acts, illusions, con games and games of chance. The most common misdirection is that of the operator/illusionist/magician, who keeps up a running patter so that your attention is distracted from what they are really doing, which isn't really magic at all.
|Chinese Linking Rings - Magic Masters.*|
As discussed in the previous blog, magic, illusion and misdirection all play into how the brain represents and processes information. If we can make the visual cortex think that something there, when it isn't, we are half way to performing a "magic trick." Likewise, misdirection relies on the fact that the brain processes familiar stimuli in a manner different than novel stimuli. Allow a rat to explore a chamber that it has experienced before, and it will usually find a convenient spot and sit down. Put it in an unfamiliar environment or add a novel feature, and the rat will spend most of its time exploring the novelty.
A similar example of novel information processing can be detected in EEG. Most EEG analysis consists of quantifying rhythms, oscillations, frequencies and spectra, since the EEG is constantly changing. However, if a tone, flash of light or photograph is presented very briefly on a computer screen, scientists can synchronize a point in the EEG with the stimulus and look for features that are time-locked to that event. We call this an "event-related potential," or ERP. ERPs are pretty small compared to most EEG activity, so it is often necessary to repeat the stimulus a few times to average out the random fluctuations of the EEG. It's been known for more than 50 years that a particular positive deflection in the ERP occurring at around 300 milliseconds after the stimulus (thus known as P300 or P3) is reduced in amplitude if the stimulus is familiar, and increased if the stimulus is unfamiliar. Thus we see that the brain "expects" familiar information, and pays more attention to unique information.
So let's look a bit closer at the idea of "expectancy." The brain has several areas that are involved in making predictions about your environment. The first area involved is cingulate cortex, located on the upper, inner surface of the two halves (hemispheres) of the cerebral cortex. The role of cingulate is typically to "guess" or make predictions of what comes next - whether reading, moving, tracking, listening - whatever the stimulus, cingulate is typically involved in making predictions. Next is the amygdala and limbic system located inside the temporal lobe. Amygdala, hippocampus, and the connected structures compare predicted (or expected) events with what actually happened. The role of hippocampus is to simultaneously provide memory of prior events, and also to store the new information regarding success of prior predictions. There are other brain ares involved, such as caudate/striatum, which provides signals indicating value or reward, and this can be very important in gambling or confidence games, but the primary brain ares involved in misdirection are these which process expectancy.
The true "magic" of an illusion or magic trick is to show the subject what they expect to see, and diverting their attention from anything that might reveal any other action or occurrence. Thus the magician's patter directs our attention to what they wish to show us, and by making that familiar they reduce our attention that would otherwise notice the unexpected events (i.e. linking the Chinese Rings) until after the event has already occurred. Gambling and confidence games invoke an additional aspect of expectancy, by assigning an arbitrarily high "value" or motivation to the expected outcome. The "mark" who expects to win a lot of money is influenced by striatal signals which reinforce the potential payoff of the prediction. An fault of our brain's expectancy circuits is a particular blindness to probability - flipping a coin 100 times means nothing to the probability of heads or tails on a single flip. However, the "Gambler's Fallacy" which represents the brain's expectancy anticipates that the more consecutive flips resulting in "heads" absolutely must mean that the next flip has a 10-to-1 chance of being "tails" when in fact the real chance is still 1-to-1.
We'll wrap up this section on Magic and the Brain with a final post on "Fooling Ourselves." In the next blog. Until then, take care of your brain, and tip the magician on your way to the buffet!
*For anyone interested in learning about and starting an amateur magic career, check local directory listings for a magic club, or check out "Magic Masters" online (http://www.magicmasters.com/store/home.php) or at one of their retail storefronts.