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Great vision? Think again


Amy Bohme
Arizona Daily Wildcat

J. Kevin O'Regan speaks about blindness Sunday morning at the Toward the Science of Consciousness conference held at Holiday Inn City Center. The week-long conference is sponsored by the UA Center for Consciousness.

By Blake Smith
Arizona Daily Wildcat,
April 11, 2000
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Researcher explains defects in human sight at consciousness conference

People who think they have perfect vision should think again.

From blind spots to smearing of images, human sight is flawed to a great extent, according to research presented at the fourth "Toward a Science of Consciousness" conference Sunday.

J. Kevin O'Regan, director of research for the National Center of Scientific Research in France, said sight has been researched for about 2,300 years - since the time of Plato.

"Plato once said that vision was not as reliable as the sense of touch," O'Regan said.

While Plato could not have foreseen discoveries in human sight defects, it appears he was correct.

O'Regan told a group of about 30 researchers from across the nation that the greatest defect in human sight is the smearing of images caused by constant eye movement.

"When you look at a scene, you move your eyes three to five times per second," he said.

While human eyes move up to 300 times each minute, O'Regan said people do not notice the blurring because of a phenomenon known as saccadic suppression.

Saccadic suppression is when the eyes essentially "turn off" during the split second that smearing of the image occurs. Another mechanism overcomes the shutdown to keep the eyes operational, and people do not notice the smearing.

O'Regan also discussed the phenomenon of a "blind spot" in people's vision.

"Our field of vision doesn't seem like it has a blind spot," he said.

O'Regan said this is best demonstrated when people close one eye and holds an object in front of them. If it is moved into the "blind spot," the object can no longer be seen.

To make up for this defect, the brain fills in the portion of the object that is not visible, he added.

"The brain has a neuro-compensation mechanism to fill in for the blind spot," O'Regan said.

While the brain compensates for the eyes in certain instances, it can act as a hindrance in others, O'Regan said.

He referenced a 1996 study in which researchers explored the issue of how much information the brain remembers about the objects people see.

Subjects were placed in-front of a picture that gradually changed. One example showed a change in the pictured person's facial expression.

"We discovered that large portions of the picture could move without (the subjects) noticing," O'Regan said.

While this experiment might be considered insignificant, it could help explain larger issues. Because the brain often remembers different things than seen, discrepancies in witness recounts of crimes could be explained with this new research, O'Regan said.

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