Scientists explain the 'flash-lag' effect

DURHAM, N.C., Oct. 14 (UPI) -- U.S. researchers say they might have explained a visual phenomenon called the "flash-lag" effect that has puzzled neuroscientists for about 100 years.

That phenomenon occurs when a flash of light is presented in alignment with a moving object but the flash is always perceived to lag behind the object.

"We decided to look at the effect empirically, based on another visual problem called the inverse optics problem, which is that the image on your retina can't be directly, logically related to what is happening in the world," said Dr. Dale Purves, director of the Duke Center for Cognitive Neuroscience.

"The solution lies in humans accumulating, over millions of years of trial and error, the information that derives from seeing a speed on the retina and making a move in response, which either works or doesn't," Purves said. "You ultimately die or you survive based on the success of what you do in the world and, if you do survive, the improvements in visual circuitry that allowed this success are passed on to the next generation."

The study that included William Wojtach, Kyongje Sung and Sandra Truong appears in the early online edition of the Proceedings of the National Academy of Science.