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Mind tricks
Mind tricks
Keren Tzuriel Harari

PHOENIX – Eight years ago, as brain researchers Susana Martinez-Conde and Stephen Macknik were driving down the Las Vegas Strip, the billboards they passed suddenly got them to rethink about the brain's capacity to process visual information. Until then, the two professors at the prestigious Barrow Neurological Institute in Arizona had addressed this question by using optical illusions. Now the signs advertizing magic acts would lead them to the next stage: Magicians are masters of manipulation, often a few steps ahead of science in using the brain's capabilities to alter the effects of visual cognition.

Martinez-Conde and Macknik had an intuition that learning magicians' techniques would help them understand how the brain's most fundamental mechanisms function.

They went on to recruit some of America's top masters of illusion, such as James Randi ("The Amazing Randi") and the duo Penn Jillette and Raymond Teller ("Penn & Teller"), who were interested in cognition studies. At the same time, to make sure they understood the profession, the two researchers learned the art of magic themselves, and were accepted in Magic Castle, the most prominent illusionists association.

"It was our one and only show," Macknik tells Calcalist. "The examiners' message was clear: You did it, but you better keep your day jobs."

Since then, their work has been centered around developing neuro-magic, a branch in brain studies they have founded. Parallel to research, they often give lectures, stage illusions and explain how difficult it is for the brain to control them.

"The visual system's task is to tell us what happens in the world on the physical level in the most accurate way possible," says Macknik. "But that's not what it actually does. It creates a simulation of the world that helps us survive. In some cases the information is very accurate, in others it's not – but in a way that is beneficial for us."

Martinez-Conde notes that some illusions will always work on everyone, no matter how frequently you watch them and what your expertise is. "In optical illusions, what's critical is the stage in the visual system in which the illusion happens," she explains. "If it's the earliest stage of the retina, then the illusion relies on circuits wired to the visual system, and in such case, even if you are aware that the illusion is there you cannot resist it."

1. So moving
Even though we confidently know it is a picture, snakes and spirals in the famous illusions spin in front of our eyes relentlessly. "These special examples create an illusion of motion because of the movement of the eye," explains Martinez-Conde. "These are very small involuntary movements called "microsaccades' and they move the picture in a way that stimulates the neural motion senses in the visual system, and it looks as if the picture is moving."

Such patterns do not exist in nature, of course, but Martinez-Conde and Macknik's study used them to determine how vital these microsaccades are for seeing, and for calculating the speed of a movement.

2. Neurons have expectations too
One of the things we're wired to do is easily recognize faces. In their lectures, Martinez-Conde presents an idyllic picutre of a cute blond boy on his father's shoulders. Everything looks perfect in the photo, until Martinez-Conde points to the boy's hand: he has two thumbs.

Shortly later she presents a photo of a family from the waist up, all are smiling and gazing at the horizon — and they all have the same face. It is very difficult to notice that. "These are illusions that are related to our expectations," explains Macknik. "We expect the faces to be different because that's what it's like in nature."

3. It's just impossible
Illusionist Jerry Andrus, who died in 2007, was an expert at creating illusions out of objects such as "The Impossible Box": a wooden chest where nothing fits together. The rear stick closes the box from the front, the front one is attached to its rear part, and Andrus would stand inside; and assuming he is a normal three-dimensional human being, this is impossible. The explanation is perspective: Change the point of view and you realize the box is L-shaped.

"This illusion demonstrates how the brain evaluates objects," says Macknik. "We see straight lines, corners and how they meet, and the brain measures them to calculate what the object is — even if there are illogical things about it. The corners and the margins of the Impossible Box are perfectly legitimate, there is nothing wrong or impossible on the local level, but something is globally wrong and this is why it is an illusion."

4. Tilting cognition
Even after watching this illusion a few times, before and after Martinez-Conde's explanations, I kept falling for it. I know these are two identical photos of the Pisa Tower that were just put next to one another. So, I know they have exactly the same incline. And still the tower in the photo on the right leans a little bit lower.

"This illusion shows us how the brain processes perspective. When we observe train tracks it appears to us that they merge on the horizon, and when we look at skyscrapers side by side it looks they near one another and meet the higher you look," she explains. "When the brain sees the two photos of the Pisa Tower it expects them to meet the higher you go, but since it's the same image, their ends don't consolidate, and one looks a bit more bent."

5. What you miss
Set to play a video, Macknik gives the audience a simple instruction: count how many balls the players of the white team pass. When the video ends, members of the audience proudly announce their counts. It's just one thing they didn't notice: the dancing black bear that appeared between the players.

"Attention works like a spotlight, and when focusing on one thing you actively repress the rest of the things around," he explains. "So if you focus your attention on the wrong thing, you might miss something important."

Here, the audience looked at the right direction, but their attention was focused on counting the passes of the ball, and thus didn't notice the bear.

"Most scientists believed this is a flaw in cognition, but we disagree," adds Macknik. "For us, that's an example the brain is doing a good job, since it fulfilled its task and ignored the rest."

6. Laughter as anesthesia
One thing Martinez-Conde and Macknik learned from magicians, but haven't studied in the lab yet: what happens at the moment of a joke's punch-line. "No one knows yet why it works — perhaps when we laugh, our attention is on the internal process and not the external senses," says Maknick. "It's a very interesting effect of cognition we want to know more about, because science knows very little about the link between attention and emotions, and it is critical for many neurological illnesses like Alzheimer. It will be the focus at the next stage of our research."

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