Brain perceives the present

[coldharvest]

http://timesofindia.indiatimes.com/HealthSci/Brain_perceives_the_present/articleshow/3118289.cms

Staring at a pattern meant to evoke an optical illusion is usually an act of idle curiosity, akin to palm reading or astrology. The dot disappears, or it doesn't. The silhouettes of the dancer spin clockwise or counter clockwise. The three-dimensional face materializes or not, and the explanation always seems to have something to do with the eye or creativity or even personality.

That's the usual cue to nod and feign renewed absorption in the pattern. In fact, scientists have investigated such illusions for hundreds of years, looking for clues to how the brain constructs a seamless whole from the bouncing kaleidoscope of light coming through the eyes. Brain researchers today call the illusions perceptual, not optical, because the entire visual system is involved, and their theories about what is occurring can sound as exotic as anyone's.

In the current issue of the journal Cognitive Science, researchers at the California Institute of Technology and the University of Sussex argue that the brain's adaptive ability to see into the near future creates many common illusions. "It takes time for the brain to process visual information, so it has to anticipate the future to perceive the present," said Mark Changizi, the lead author of the paper, who is now at Rensselaer Polytechnic Institute. "One common functional mechanism can explain many of these seemingly unrelated illusions." His co-authors were Andrew Hsieh, Romi Nijhawan, Ryota Kanai and Shinsuke Shimojo.

One fundamental debate in visual research is whether the brain uses a bag of ad hoc tricks to build a streaming model of the world, or a general principle, like filling in disjointed images based on inference from new evidence and past experience. The answer may be both. But perceptual illusions provide a keyhole to glimpse the system.

When shown two images in quick succession, one of a dot on the left of a screen and one with the dot on the right, the brain sees motion from left to right, even though there was none. The visual system has apparently constructed the scenario after it has been perceived, reconciling the jagged images by imputing motion.

In an experiment originated by Nijhawan, people watch an object pass a flashbulb. The timing is exact: the bulb flashes precisely as the object passes. But people perceive that the object has moved past the bulb before it flashes. Scientists argue that the brain has evolved to see a split second into the future when it perceives motion. Because it takes the brain at least a tenth of a second to model visual information, it is working with old information. By modelling the future during movement, it is "seeing" the present.

Changizi and his colleagues hold that it is a general principle the brain applies to a wide variety of illusions that trick the brain into sensing motion.

Timothy Hubbard, a psychologist at Texas Christian University, said the principle of perceiving the present was sound, adding, "If a person's response to an object, to catch, hit, block, whatever, is to be optimal, that response should be calibrated to where the object would be"— not a split second earlier, when the perception occurred.

This is why identical squares arranged around the center of a spiked-wheel image appear misshapen, said Changizi. The sides of squares closer to the center appear to bulge. The sides farther out appear shorter. The radiating lines in the pattern trick the brain into perceiving motion forward, so it projects objects forward, making those nearer the center appear closer to the eye. The same effect can be seen by leaning forward toward a precise checkerboard. The image seems to bulge forward, this time because the eyes are moving.

[michelle in alaska]

*note to self: you cannot edit. this is the tfhc*

coldharvest, that was a verrry interesting article. but I usually associate the future being that which is unseen. how would this apply?

[Sri Lanky]

Most things in the present are unseen.

[michelle in alaska]

Most things in the present are unseen.

Great. NOW you tell me.

That may explain alot of my present angst. :)

[Caliban]

In an experiment originated by Nijhawan, people watch an object pass a flashbulb. The timing is exact: the bulb flashes precisely as the object passes. But people perceive that the object has moved past the bulb before it flashes.

That Nijhawan is a sneaky cnut

[friendlyskies]

Well, that would explain why some people feel like none of this is real. It's not, it's based on your extrapolation of a future reality based on a set of data that existed a fraction of a second ago; we are all in a slightly altered - not alternate - universe that is partially of our own personal design, based on past experiences and preconceptions as well as the reality we all share.

[Ultra Swain]

isnt this what causes deja vu? Your perception is a bit faster than you can cognitively handle so things seem like a a repeat.

[Sri Lanky]

Reality is too fast for our perception.

[coldharvest]

Reality is too fast for our perception.

You Sir are well down the path.

[nowonmai]

I will cite this as evidence in any future speeding tickets I receive. I was in my own reality and any perception that the hofficer had that I was speeding was based on a presumptive future that didn't actually happen. Wish me luck.

[Ultra Swain]

I will cite this as evidence in any future speeding tickets I receive. I was in my own reality and any perception that the hofficer had that I was speeding was based on a presumptive future that didn't actually happen. Wish me luck.

Jesus Christ. If you are gonna do it with that attitude it will never work.

[nowonmai]

I jest. In reality I'd commit seppuku if I ever suffered the indignity of being caught.