428 - A bunch of stuff

The links will take you back to the original articles if they're still accessible, (and more links). If not, here's the articles.


Study Reveals How Magic Works

Scientists are figuring out how magicians fool our brains in research that also helps uncover how our mind actually works. A great deal of what scientists now understand about how the human visual system works stems from research into our susceptibility to optical illusions. "It made sense to look at magicians to advance knowledge of human cognition, since magicians have been working on figuring out how certain principles of psychology work for hundreds of years," said researcher Gustav Kuhn at the University of Durham in England, a cognitive psychologist who has also performed magic the past couple decades.

"Magicians really have this ability to distort your perceptions, to get people to perceive things that never happened, just like a visual illusion," he added.
The researchers looked into a magic trick called the "vanishing ball," in which a ball apparently disappears in midair. It's done by faking a throw while keeping the ball secretly palmed in the magician's hand.

Kuhn videotaped himself performing two versions of the illusion. In the "pro-illusion" version, on the fake throw, his gaze and head followed an imaginary ball moving upwards. In the "anti-illusion" version, Kuhn's eyes stayed on the hand concealing the ball. Roughly two-thirds of volunteers watching the pro-illusion version on television had a vivid recollection of the ball leaving the top of the screen. "Often they claimed someone at the top of the screen caught the ball," Kuhn told LiveScience. In comparison, only a third of the people viewing the anti-illusion version experienced that illusion.

Kuhn and his colleagues measured the eye movements of volunteers during the experiment. Surprisingly, they found that when people believed they saw the ball vanish, most claimed they spent their entire time looking at the ball, yet most actually glanced at the magician's face prior to following the ball to help them perceive the ball's location. "Even though people claimed they were looking at the ball, what you find is that they spend a lot of time looking at the face. While their eye movements weren't fooled by where the ball was, their perception was. It reveals how important social cues are in influencing perception," Kuhn said.
"As we are looking at the world, we have this impression that what we see is the real world. What this tells us is the way we see the world is more strongly dominated by how we perceive it to be rather than what it actually is," Kuhn added. "Even though the ball never left the hand, the reason people saw it leave is because they expected the ball to leave the hand. It's the beliefs about what should happen that override the actual visual input."

In the future, the researchers plan to investigate how other magic tricks fool the brain. Kuhn and his colleagues will report their findings in the Nov. 21 issue of the journal Current Biology.


AND THEN THERE WAS THIS ARTICLE ALSO-----

How Sight and Sound Can Trick Your Brain

Auditory and visual information in the brain can conspire to trick us into seeing things that are not there, according to new research that suggests our senses are more intimately linked than previously suspected. Researchers found that subjects shown a single flash of light sandwiched between two tones in quick succession reported seeing an illusory second light flash. The finding, detailed in the April 12 issue of the Journal of Neuroscience, suggests the brain takes only a matter of milliseconds to combine auditory and visual information, much faster than scientists thought possible.

A direct link

“Usually, it’s thought that the way different senses talk to each other is they go to a way-station higher up where both senses combine, and then that higher order center sends back information to one sense or the other,” said study team member Jyoti Mishra, a graduate student in the lab of Steven Hillyard at the University of California, San Diego. But the quick rapport between the two brain areas suggests there is a more direct link, she said.

The finding supports previous anatomical studies in monkeys which found neural pathways directly linking the auditory and visual portions of the brain. “People have traced out the connections and found evidence of a direct link. But there has not been any functional evidence that [communication] really happens this fast,” Mishra told LiveScience. “Our study provides that functional evidence.” In the study, 34 participants sat through the tone-light-tone test about 300 times. Every subject experienced the illusory light flash, but some experienced it more often than others. “How much they see the illusion can range from 10 to 90 percent of the time the trials are shown to them,” Mishra said in a telephone interview.

Predicting the illusion

The researchers also found they could predict when the subjects would experience the visual illusion by looking at their brain's electrical activity during the experiment. Only those people whose brains showed an electrical boost in their auditory cortex after the second tone reported seeing the illusory flash.

Thus, the brain wiring and the strength of auditory and visual integration might differ between individuals, or even vary over time, the researchers say. “It suggests that there are consistent differences in the neural connectivity that are possibly shaped during one’s development and through experience,” Mishra said.


AND THEN THIS ONE....

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. 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.

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."

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."