The lie of the tiger( The experimental team which also in...)

The experimental team, which also included George Sperling, Ph.D., of the University of California, Irvine, department of cognitive science, and USC graduate student Luis A. Lesmes, began with computer displays in which alternating green and red stripes moved across a screen. The team then systematically purified the displays, removing brightness differences from the green and red stripes, making them "isoluminant."

Using complex displays with special mathematical properties, the researchers discovered that, unlike first- and second-order motion, color motion depends critically on the location of the dominant features in the display but doesn't use information about which eye is providing the information.

The team also definitively confirmed that third-order, figure-ground perception is the only way isoluminant color motion can be perceived. They did so by designing and creating a striking illusion of "motion standstill."

The moving objects were not tiger stripes but a series of computer-generated moving red and green color bars. After appropriate adjustment of the saturation of the green bars relative to the red bars, the display appeared stationary to 53 out of 53 observers, even though the bars continued to move.

"The strategy we used in these studies is similar to that used in physics," commented Lu, who was originally trained as a physicist. "Ordinarily, moving objects stimulate all three motion systems. In the laboratory, we can create a 'pure stimulus' that only stimulates one particular motion system. By studying a 'pure stimulus', like an isolated atom, we can reveal the secrets of the human brain."

According to Lu, the methodology and results from this study will provide a basis for a broad class of neurophysiological investigations on high-order brain functions. The computational algorithms will be incorporated into models of human visual motion perception.

Eventually, the computer models might be replicated for robotic d
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Contact: Eric Mankin
mankin@usc.edu
213 740 9344
University of Southern California
5-Jul-1999