CAMDEN How the brain perceives color is one of its more impressive tricks. It is able to keep a stable perception of an object's color as lighting conditions change.
Sarah Allred, an assistant professor of psychology at RutgersCamden, has teamed up with psychologists from the University of Pennsylvania on groundbreaking research that provides new insight into how this works.
Allred conducted the research with Alan L. Gilchrist, a professor of psychology at RutgersNewark, and professor David H. Brainard and post-doctoral fellow Ana Radonjic, both of the University of Pennsylvania. Their research will be published in the journal Current Biology.
"Although we recognize easily the colors of objects in many different environments, this is a difficult problem for the brain," Allred says. "For example, consider just the gray scale that goes from black to white. A white piece of paper in bright sunlight reflects thousands of times more light to the eye than a white piece of paper indoors, but both pieces of paper look white. How does the brain do this?"
The process of seeing an object begins when light reflected off that object hits the light-sensitive structures in the eye. The perception of an object's lightness (in terms of color shade) depends on the object's reflectance. Objects that appear lighter reflect a larger percentage of light than those that appear darker.
Allred says the brain processes perceptual differences between black and white objects even when illumination of the object changes. If the brain did not do this, it would fail to distinguish color shade in different light.
In general, white objects reflect about 90 percent of the light that hits them, and black objects reflect about three percent, a ratio of 30-to-1, she explains.
"However, if you look at the intensities of light that enter the eye from a typical scene, like a field of lilies, that ratio is much higher, usually
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