Sleights of Mind: What the Neuroscience of Magic Reveals about Our Everyday Deceptions by Stephen L. Macknik
My rating: 4 of 5 stars

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Sleights of Mind explains magic tricks by telling one about the shortcuts, limits, and programming of brain (and attendant sensory systems) that facilitate such tricks. The reader needn’t be concerned that the book will spoil all the illusionists’ secrets for one. The authors carefully demarcate the beginnings and endings of spoiler sections that explicitly explain tricks. This allows a reader to skip over such sections if one doesn’t want to know the trick. I suspect few readers do skip the spoiler sections because that’s where the rubber meets the road in terms of the neuroscientific concepts being discussed. The spoiler sections are an attempt to comply with the magician’s code (the neuroscientist authors became magicians themselves) and to maintain a good relationships with the many magicians (some, like Teller or the Amaz!ng Randi, quite famous) who cooperated in the writing of the book.

Over 12 chapters, the authors explain the neuroscience of how various classes of illusion work. Most of the chapters address a specific class or subclass of illusion. The first few chapters deal with visual illusions. We look at the world in what seems like crystal clarity (at least with glasses on or contacts in), but there are many limitations and gaps in our visual processing system. While it seems like we are directly seeing the world around us, in point of fact, our visual experience is a product of the brain reconstructing information that the eyes take in—and it doesn’t do it as perfectly as our brain tricks us into believing. As the authors state it, “The spooky truth is that your brain constructs reality, visual and otherwise.” Chapter 3, deals with illusion in art, which is little outside the theme of the book, but it offers an opportunity to explain some intriguing facts about how the brain and eyes work in concert.

The next couple chapters (Ch. 4 and 5) deal with cognitive illusions. Just like our visual system, our conscious minds save energy by engaging in short-cuts that disguise the mind’s limits while offering the possibility of manipulation. The brain also works hard to reconcile what appear to be inconsistencies, and often this reconciliation leads us astray. Misdirection is discussed in detail. Our minds are primed to let certain actions and sensory inputs draw its attention, and humans are awful at paying attention to more than one input stream at a time. Teller explains that, “Action is motion with a purpose.” So, if one can give one’s movement a purpose (even scratching one’s chin) it will be ignored while movements seemingly without purpose are anomalous and draw attention. The authors introduce the reader to mirror neurons—the part of our brains that take observations of another’s actions and makes forecasts about that person’s intent. This system is highly hackable by magicians.

Chapter 5 informs us that we aren’t as good at multitasking as we think—which is to say we completely stink at it but tend to think we are awesome multi-taskers. The gorilla experiment is offered as a prime example of this situation. In the gorilla experiment, about half-a-dozen people, moving around randomly, pass a ball / balls among themselves. The subject is asked to count the number of passes. In the middle of this activity a man in a gorilla suit walks through the middle of the rapidly moving passers. When asked whether they saw the gorilla, most people say they didn’t (and those who do see the gorilla invariably offer a count of passes that is vastly off the mark.) [If this is either unclear or unbelievable, you can YouTube it.]

Chapter 6 examines multi-sensory illusions. The quintessential example is how our brains lead us believe that the sound of a ventriloquist’s voice is coming from the moving lips of a dummy. (Also, it seems like voices are coming from the lips of actors on-screen in the movies, even though the speakers are probably off to the side in the walls or ceiling.) Synesthesia (cross-wiring between senses and brain such that some people may always see the number 5 in red or hear a C-sharp in green) is introduced to the reader.

Chapter 7 explores the illusions of memory. Just as with our vision and attention, our memories aren’t as indelible as they seem to be. We think we’re calling up a transcription of the events of our lives, but really we’re remembering the last remembrance of said event. This can lead to a migration / distortion of events in the same manner as the kid’s experiment whereby one whispers a phrase into the ear of the kid in the next chair and it traverses the classroom. The original sentence “The cat is on the windowsill” invariably becomes something like “Lenny Kravitz steals puppies from the till.” (Have you ever experienced a situation in which a person remembers the details of an event substantially differently from yourself even if the broad brushstrokes are the same?) Some entertainers use pneumonic tricks to convince audiences that they have supernatural mental abilities when—in fact—they have merely turned understanding of memory to their advantage.

Chapter 8 considers how in-built expectations and assumptions are exploited by magicians and mentalists. Again, these methods work because our brains employ all sorts of energy-saving shortcuts. For example, our brains often do the same thing as Google’s search engine—filling in the blanks by taking advantage of one’s experience to avoid the need for costly cognitive processing.

Chapter 9 explains that our “free choices” are often not so “free” as we think. One of the most disconcerting, yet intriguing, facts to come from the onslaught of brain imaging studies since the 1990’s is that our decisions are made on a subconscious level before our conscious minds are even aware the decision has been made. Prior to this, we’d always been under the misapprehension that we are consciously making all these decisions–big and small–because the conscious mind is just a big credit stealer (to be fair, the conscious mind doesn’t recognize that it’s so out of the loop in decision-making.) So many of our decisions are made in predictable ways by emotional / automated responses, and mentalists use that fact to their advantage.

Chapter 10 is a catchall for topics that didn’t fit into earlier chapters, including hypnosis, superstitions, and the gambler’s fallacy (i.e. the idea that a roulette number that hasn’t come up in a while [or slot machine that hasn’t paid off recently] is bound to pay soon—regardless of the probability distribution that actually rules the outcome.)

The remainder of the book tells the story of the author’s try-out for a magic society and discusses the question of whether knowing the neurological and psychological roots of magic tricks will kill magic as a source of entertainment. I found the latter to be the more interesting discussion. The authors are optimistic about magic’s survival, and offer good reasons. After all, almost nobody believes that magicians are conducting supernatural activities [not even people who take some wildly unsubstantiated beliefs as givens.] Even knowing how the tricks work doesn’t create the ability to see through the tricks because so many of the factors that magicians exploit operate on a subconsciously programmed level, and such proclivities would have to be trained away. People who want to enjoy the spectacle of magic aren’t likely to go to the trouble of training themselves in that way.

I enjoyed this book even though I’m not particularly a fan of magic—though I did find myself watching quite a few YouTube clips of the magicians mentioned in the book. If you’re interested in how one’s mind and sensory systems work, and the limitations of those systems, you’ll find this book worthwhile. If you’re into magic, you’ll like it all the more so.

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