Illusions: Fooling the Brain

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)

Clad in a tuxedo, the tall and bearded conjurer tosses the ball up. Once, twice, thrice — voila! The ball disappears midflight. You’re absolutely sure that your gaze didn’t waver from it, so where did the ball go? Of course, it didn’t actually disappear forever — you know that — but your senses were fooled, and you aren’t sure how. This is the famous “Vanishing Ball” illusion, and it’s pretty impressive.

Magicians long ago mastered the art of deception. The question is, how did they get so good at it? That is what many neuroscientists and cognitive psychologists are trying to find out by studying the science of magic or, as some call it, neuromagic.

“Fifty years ago, no one had formal training in the neurosciences,” says Stephen L. Macknik, director of the Laboratory of Behavioral Neurophysiology at Barrow Neurological Institute in Phoenix, Arizona. “On the other hand, magic has been performed for over 2,000 years by smart people. While magicians haven’t used the scientific method, they have studied the human brain a lot longer than scientists have. And they have discovered important things.”

Macknik’s colleague Susana Martinez-Conde, director of the Laboratory of Visual Neuroscience at the institute, expands on the idea. She explains that “The visual sciences have always borrowed from the visual arts. Some illusions, perceptional phenomena we know now and take as a given in visual sciences — rules of perspective, for example — didn’t come from science. They were discovered by artists during the Renaissance.”


Magicians use a combination of tools, such as illusions, special effects, and secret devices, to produce results that seem to defy the laws of physics. There are typically three main types of illusion: optical, visual, and cognitive. Think of it like this: Visual illusions occur when our fallible brain constructs a false perception of our physical reality. The “Colored Dress” trick by Las Vegas magician Johnny Thompson — aka the Great Tomsoni — perfectly demonstrates how magicians make use of visual illusions.

Here’s how the trick is played out onstage. Tomsoni’s gorgeous assistant, probably clad in a short white dress, is bathed in the spotlight. Tomsoni claps his hands. The spotlight dims for a jiffy, only to transform into a glistening red light. Presto! The woman — as well as the dress — is now red. You think — wow, is that it? However, Tomsoni’s trick is not over yet. He claps again. This time, the lights dim for a few moments, and the white spotlight is back. Guess what? Her dress is still red.

Tomsoni deceives our senses very subtly. Since the assistant is an attractive woman, the audience becomes fixated on her, so much so that they burn a deep afterimage of her into their retinas. An afterimage is something we experience on a daily basis. If you stare at a waterfall for a few minutes and then transfer your gaze to nearby rocks, they seem to flow, if only for a few moments.

When you continue to gaze at the red-lit dress, neurons in the brain, whose job is to perceive the color red, get adapted to the red-lit dress by being less active. Such neurons are better adapted to the red stage and will have a bigger afterdischarge once the light is turned off. The afterimage of the red woman in a red dress lingers for about a tenth of a second. During this little interval, Tomsoni brings out the trump card. The white dress, held on to the assistant with the help of Velcro and invisible cables leading under the stage, is pulled off her body and whisked into a trap door. Voila — the lights come on, and the bright red dress the woman had been wearing underneath becomes exposed.

Macknik says, “The retinal afterimage of the dress makes it appear red so that you can see the woman during the 100 milliseconds or so when the white dress is removed. The physical reality (lights are off) differs from the perception (you can see the lady), and therefore that component of the trick is a visual illusion.”

Now, cognitive illusions fiddle with the brain’s higher functions, such as memory and attention. For most magicians, diverting our attention — called misdirection — from the method to the effect is a way of achieving the desired result. During overt misdirection, a magician drives the audience’s attention away from where the action is really taking place by shifting its gaze. During covert misdirection, the audience is looking at the method, but its attention is elsewhere.

Why is misdirection successful? Cognitive neuroscience may offer some insight. It turns out that the answer has to do with change blindness and inattentional blindness. Remember those newspaper trivia pages, the ones where you’re shown two almost identical images and you’re tasked with finding the difference? Of course, one glance is not enough to pinpoint the differences — that’s what change blindness is. Inattentional blindness, on the other hand, is when you miss things that are predominantly present in a scene. Daniel J. Simons, professor of psychology at the University of Illinois at Urbana-Champaign, says, “These concepts illustrate how we are only aware of a subset of our visual world at any time. More importantly, they run counter to our intuitive belief that whenever something important happens right in front of us, it will automatically grab our attention. We feel that we are aware of our surroundings, but we are only aware of those parts of our world that fall into the focus of our attention. We don’t realize how much we’re missing.”

Simons’ famous “Invisible Gorilla” experiment aptly illustrates the limits of awareness. Participants were shown a video of six people — three in white shirts and three in black — passing basketballs around. They had to keep count of the passes made by the people in white shirts. At one point, a woman dressed as a gorilla walked into the middle of action and thumped her chest. Half the participants in the study failed to notice.

Optical illusions are defined by visually perceived images that differ from objective reality. Bluntly speaking, they embody aspects of visual and cognitive illusions.


The science of magic has a lot to offer. Martinez-Conde believes that insights from the field can apply in many areas, including education. “Magicians have the capacity to control our attention. They’re controlling our attention very carefully and directing it to whatever they want us to be focusing on. If teachers could do the same thing — divert students’ focus to what matters — that would be great,” she notes.

The benefits could be channeled into the medical field as well. “In patients with cognitive decline and neurological trauma, rehab therapists have a tough time getting them to focus,” Macknik says. “Their rehab therapist needs them to focus their attention on the right thing at the right time. These patients could see a much stronger clinical benefit out of this research.”

He adds that magicians control our emotions in order to control our attention, such as by telling jokes. He contends that magicians don’t tell jokes just for the sake of entertainment. “They drop them at specific times; they are part of the trick. There is a strong connection between emotions and attention. We know fear controls attention. But scientists know little about how humor controls attention,” Macknik says. “This could potentially help us understand the underpinnings of a disease like Alzheimer’s that has a strong emotive component.” The duo is focusing on this branch of research.

The current research is expected to offer insight into perception and cognition. Ron Rensink, an associate professor in the psychology department at the University of British Columbia who studies card tricks, says, “The science of magic is beginning to take on a definite form, with studies becoming more rigorous and connecting to what we know of human perception and cognition. There are several interesting directions emerging, including decision-making, the development of motor skills (magicians have highly practiced abilities), and studies into what does or does not create a sense of wonder (i.e., which kinds of events seem ‘magical’ and which do not).”

When it comes to the science of magic, there is just so much more than meets the eye!

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)


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