NASHVILLE, Tenn. - Picture a marching band on the football field during halftime. With precise steps, some band members turn and march in a different direction than the rest, spelling out a school's letters or a mascot's shape. Scientists have known for years that to perceive figures against such a busy background, human vision uses color, brightness and direction of motion. But startling new findings reported by Vanderbilt researcher Randolph Blake in the May 14 issue of Science magazine indicate that the human brain can also use the precise timing of subtle visual changes to group elements into objects.
"People can compute changes in the direction of movement of many distinct parts of a scene at once, and can tell from the timing of these changes which parts belong to the same object," said Blake, a professor of psychology and investigator for Vanderbilt's John F. Kennedy Center for Research on Education and Human Development, who conducted his recent research with Vanderbilt graduate student Sang-Hun Lee. "This is the most convincing demonstration yet that the human visual system can use timing information alone to form coherent objects from features of a scene that change at the same time."
For their study, "Visual Form Created Solely from Temporal Structure," Blake and Lee created on a computer video screen a dense array of pinwheel-like objects, each spinning clockwise or counterclockwise. Each pinwheel changed its direction of rotation at random time intervals. When a cluster of pinwheels changed their directions at the same time, they appeared to form a coherent shape that stood out from the remaining pinwheels.
"Viewers were able to distinguish the synchronized group of pinwheels from the
rest. This ability implies that we can compute changes in direction in the
movement of many distinct parts of a scene and then identify the boundaries
where the timing of these changes differs significantly," explained Blake. "In
one respect, these are
Contact: Peggy Shaw