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December 23, 1999

Shapes May Affect Color Perception

Filed at 10:31 a.m. EST

By The Associated Press (from APOnline)
A new study suggests the human brain knows a lot more about science and the properties of light than you might believe. 

When you see holiday lights reflected on a wall, the colors you perceive may not be what's really there. The study published today in the journal Nature shows that the brain automatically compensates for what direction the lights are coming from, meaning you see a color closer to that of the light bulb than what actually comes bouncing off the wall. 

``Our brains know more about physics and light reflection than we consciously realize,'' said Dan Kersten, a psychologist at the University of Minnesota in Minneapolis. ``Our brain can take into effect the physics of the light that strikes the object to determine the color.'' 

Kersten said the brain assigns color to an object only after taking into account how light bounces off of it. 

Experts said his results were not a surprise. ``But it's nice to see a clear-cut confirmation,'' said psychologist Vilayanur Ramachandran, another specialist in the field at the University of San Diego. 

Kersten said his research could help engineers create more realistic computer games and virtual reality devices by gaining a better understanding of how we perceive light bouncing off objects. 

The experiment was based on an optical illusion. 

Researchers attached a white card to a magenta card, so that the cards faced each other like walls in the corner of a room. In that situation, the brain expects the white to appear pink because of light reflecting off the magenta card. 

Participants were asked to look at the cards twice, once through a normal lens and once through a prism that made it look as if the cards were folded away from the viewer, like an aerial view of a roof. 

During each view, the participants were asked to describe the shade of pink on the white card by matching it to one of seven paint samples. 

Of course, the true shade was the same for both views. But the viewers said it was lighter when they thought they were looking into the ``corner'' arrangement than when they thought they were looking at the ``roof'' setup. 

Why? The brain automatically lightened the pink to compensate for the reflection of the magenta card when it perceived the ``corner,'' the researchers said. 

Since the brain did not expect any reflected magenta light when looking at the ``roof,'' it perceived a darker shade of pink, closer to the color that was actually there.