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Inside the Secrets of Illusions & Memory

Michael Sweeney is the author of “Brainworks: The Mind Bending Science of What You See, How You Think, and Who You Are,” the companion book to Brain Games, a three-part series on the National Geographic Channel premiering this weekend around the globe. The book and show both make you the test subject in an array...

Michael Sweeney is the author of “Brainworks: The Mind Bending Science of What You See, How You Think, and Who You Are,” the companion book to Brain Games, a three-part series on the National Geographic Channel premiering this weekend around the globe. The book and show both make you the test subject in an array of astonishing challenges and experiments. Here, Sweeney discusses some of the book’s most surprising optical illusions, and how learning the inner workings of the brain has made him a happier person.


Did writing about how the brain works come naturally to you?

Even with my method of trying to become as well-read and to talk to as many people as I can, there are still things about this book that were really hard for someone who’s not a neuroscientist to write. This really stretched my brain and made it hurt, terribly.

The problem is even science doesn’t really know all the ways the brain does what it does. I’m stunned at how complicated it is. [For example with color vision,] I do my very best work trying to explain it in plain English [and my editor just shakes his head and says,] “nice try there, guy.”

Hardest thing I’ve ever tried to write about–ever: trying to explain how color vision works.


Did anything in the book freak you out?

There’s a picture of wheels of blue and yellow. This is a static image, but as you look at it, it’s moving. And your rational mind says that can’t be moving, that’s ink on paper, and that yet, there it is. And so your eyes tell you one thing and your brain tells you another, and they can’t both be right.

This is the phenomenon of adaptation. When your cone cells become tired of looking at the same color, they will fire it more weakly to the brain after a while, and therefore the color they’re associated with (and here I go trying to explain color vision, and I’ve already told you its really hard) but [the other color in the] pair they’re associated with–red/green, blue/yellow–fires more strongly. All of a sudden if one color on one cone starts firing differently than it did a moment before, you can have this illusion of movement as the color changes and shifts from cone to cone to cone to cone. And so these wheels turn if we stare at them. Especially in our peripheral vision because the cones are concentrated in the center of your vision, and they’re scattered more widely in the edges.

It moves! and yet it doesn’t move. I feel like Galileo here.

(Related: The World’s Oldest Optical Illusion Found?)


What was the most surprising thing for you?

When I did the research about how memories actually are formed, I learned that memories are stored in various parts of the brain associated with the initial sensations. So the color is stored one place and the sound is stored one place, and the associations are stored throughout. So when you call up a memory, you’re not just pulling a video tape out of a cabinet, you’re pulling jigsaw puzzle pieces out of boxes stored in all sorts of closets, and you’re putting the puzzle together.

And then–this is what really threw me–we think that these memories are permanent. They’re not.

When you pull up these bits of memory from random access in your brain, they get stuck to other things you associate with them. So they’re all jumbled up together and I may put two pieces together that don’t belong together, and then refile them, and from then on, I’ve created a memory.

By golly, I read that and I [was] stunned at how easy it is to either remember things that you think you knew, but remember them wrongly, or to have someone suggest something to you and that screws you up. [In fact,] New Jersey just passed a law that makes eye witness testimony more subject to questioning for its validity in court testimony.


Should this information change how we treat our minds and our perception?

It’s a post-modernist world. I teach this with my graduate students. One of the things we have to wrestle with is “how do we know what we know.” You shouldn’t have total confidence in virtually anything that you know. Because the world’s not out there, the world’s in here. This is our total perception.

If it’s true that these illusions are evidence that the brain is filling in gaps to make nice seamless narratives, then the brain is actively constructing reality. And  if that’s true, then my constructed reality is valid for me but it may be different than your constructed reality which is valid for you.


That sounds like it could lead some people into aimless despair…

You could say, well on one hand you’re just the victim of all these random electrons firing in your brain and it’s all a mechanical process, but I say no, I’m active, I get to emphasize some thing over another, and choose some thing over another, and if I get things wrong? That’s part of who I am. I’m constructing my vision not only of the world but of myself and I’m comfortable with that.

So I am much less certain about the world, and much happier about it.

[Editor’s Note:  Or as Dumbledore once said to Harry Potter, “Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?”]


Listen to another conversation with Michael Sweeney and Boyd Matson on NG Weekend:

[audio:|titles=Michael Sweeney on NG Weekend]


More Mind Bending Fun

Tune In to Brain Games on the National Geographic Channel Sunday, October 9th

Watch Brain Games Video Clips

Try Brain Games Puzzles and More

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Meet the Author

Author Photo Andrew Howley
Andrew Howley is a longtime contributor to the National Geographic blog, with a particular focus on archaeology and paleoanthropology generally, and ancient rock art in particular. Over 11 years at the National Geographic Society, Andrew worked in various ways to share the stories of NG explorers and grantees online. He also produced the Home Page of for several years, and helped manage the Society's Facebook page during its breakout year of 2010. He studied Anthropology with a focus on Archaeology from the College of William & Mary in Virginia. He has covered expeditions with NG Explorers-in-Residence Mike Fay, Enric Sala, and Lee Berger. His personal interests include painting, running, and reading about history. You can follow him on Twitter @anderhowl and on Instagram @andrewjhowley. Learn more at