- Yahoo!
- My Yahoo!
- Mail
- More
  - Travel
  - Finance
  - Entertainment

- New User? Sign Up
- Sign In
- Help

Yahoo! News
Yahoo! News Search Search:

##### Primary Navigation

- Home
- U.S.
- Business
- World
- Entertainment
- Sports
- Tech
- Politics
- Elections
- Science
- Health
- Most Popular

##### Secondary Navigation

- Science Video
- Weather News
- Space & Astronomy
- Animals & Pets
- Dinosaurs & Fossils
- Biotech
- Energy
- Environment

Search:
Advanced

#
Key to All Optical Illusions Discovered

Jeanna Bryner
Senior Writer
LiveScience.com 36 minutes ago

Humans can see into the future, says a cognitive scientist. It's nothing like the alleged predictive powers of Nostradamus, but we do get a glimpse of events one-tenth of a second before they occur.

ADVERTISEMENT

And the mechanism behind that can also explain why we are tricked by optical illusions.

Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York says it starts with a neural lag that most everyone experiences while awake. When light hits your retina, about one-tenth of a second goes by before the brain translates the signal into a visual perception of the world.

Scientists already knew about the lag, yet they have debated over exactly how we compensate, with one school of thought proposing our motor system somehow modifies our movements to offset the delay.

Changizi now says it's our visual system that has evolved to compensate for neural delays, generating images of what will occur one-tenth of a second into the future. That foresight keeps our view of the world in the present. It gives you enough heads up to catch a fly ball (instead of getting socked in the face) and maneuver smoothly through a crowd. His research on this topic is detailed in the May/June issue of the journal Cognitive Science,

Explaining illusions

That same seer ability can explain a range of optical illusions, Changizi found.

"Illusions occur when our brains attempt to perceive the future, and those perceptions don't match reality," Changizi said.

Here's how the foresight theory could explain the most common visual illusions - geometric illusions that involve shapes: Something called the Hering illusion, for instance, looks like bike spokes around a central point, with vertical lines on either side of this central, so-called vanishing point. The illusion tricks us into thinking we are moving forward, and thus, switches on our future-seeing abilities. Since we aren't actually moving and the figure is static, we misperceive the straight lines as curved ones.

"Evolution has seen to it that geometric drawings like this elicit in us premonitions of the near future," Changizi said. "The converging lines toward a vanishing point (the spokes) are cues that trick our brains into thinking we are moving forward - as we would in the real world, where the door frame (a pair of vertical lines) seems to bow out as we move through it - and we try to perceive what that world will look like in the next instant."

Grand unified theory

In real life, when you are moving forward, it's not just the shape of objects that changes, he explained. Other variables, such as the angular size (how much of your visual field the object takes up), speed and contrast between the object and background, will also change.

For instance, if two objects are about the same distance in front of you, and you move toward one of the objects, that object will speed up more in the next moment, appear larger, have lower contrast (because something that is moving faster gets more blurred), and literally get nearer to you compared with the other object.

Changizi realized the same future-seeing process could explain several other types of illusions. In what he refers to as a "grand unified theory," Changizi organized 50 kinds of illusions into a matrix of 28 categories. The results can successfully predict how certain variables, such as proximity to the central point or size, will be perceived.

Changizi says that finding a theory that works for so many different classes of illusions is "a theorist's dream."

Most other ideas put forth to explain illusions have explained one or just a few types, he said.
The theory is "a big new player in the debate about the origins of illusions," Changizi told LiveScience. "All I'm hoping for is that it becomes a giant gorilla on the block that can take some punches."

- Video: How to Time Travel
- Study Reveals How Magic Works
- Top 10 Mysteries of the Mind

- Original Story: Key to All Optical Illusions Discovered

Visit LiveScience.com for more daily news, views and scientific inquiry with an original, provocative point of view. LiveScience reports amazing, real world breakthroughs, made simple and stimulating for people on the go. Check out our collection of Science, Animal and Dinosaur Pictures, Science Videos, Hot Topics, Trivia, Top 10s, Voting, Amazing Images, Reader Favorites, and more. Get cool gadgets at the new LiveScience Store, sign up for our free daily email newsletter and check out our RSS feeds today!

- Email Story
- IM Story
- Printable View

#### RECOMMEND THIS STORY

Recommend It: Not at All Somewhat Moderately Highly Very Highly

Average (Not Rated)

» Recommended Stories

### Science News

- Kennedy's brain surgery is risky, doctors say AP
- Space shuttle closes in on space station AP
- Robotic arm of Mars spacecraft leaves 'footprint' AP
- Cost drives Senate climate debate AP
- The Nation's Weather AP

### Most Viewed - Science

- Space shuttle closes in on space station AP
- Robotic arm of Mars spacecraft leaves 'footprint' AP
- Rare uncontacted tribe photographed in Amazon Reuters
- 'Aliens' Ogled My Teen Daughters! LiveScience.com
- New Images From Phoenix Lander May Show Martian Ice SPACE.com

### Science Video

- Discovery shuttle blasts off BBC - Sun Jun 1, 11:20 PM ET
- Science Rocks! ABC News - Sun Jun 1, 1:02 PM ET

- Discovery lifts off with Japanese space lab AFP - Sat May 31, 7:03 PM ET
- Shuttle mission CNN - Sat May 31, 8:46 AM ET

Sponsored Links

( What's this? )

- Refinance $300,000 for Only $965/Month
  $300,000 Mortgage for only $965/month. Save $1,000's - No obligation.
  www.HomeLoanHelpLine.com
- Free Credit Report with All 3 Scores
  Free 3-bureau Credit Report – includes Transunion, Equifax, Experian.
  FreeCreditReportsInstantly.com
- No Time for School? Graduate Online
  Get a Degree in as Few as 2 Yrs- Graduate Faster with Online Classes.
  www.ClassesUSA.com

Yahoo! - My Yahoo! - Mail

Search:
Advanced

### Primary Navigation

- Home
- U.S
- Business
- World
- Entertainment
- Sports
- Tech
- Politics
- Science
- Health
- Travel
- Most Popular
- Odd News
- Opinion

Copyright © 2008 Yahoo! Inc. All rights reserved. Questions or Comments Privacy Policy -Terms of Service - Copyright/IP Policy