A new study by researchers at UC Davis shows how our very short-term "working memory," which allows the brain to stitch together sensory information, operates. The system retains a limited number of high-resolution images for a few seconds, rather than a wider range of fuzzier impressions.
Humans rarely move their eyes smoothly. As our eyes flit from object to object, the visual system briefly shuts off to cut down visual "noise," said Steven J. Luck, professor of psychology at the UC Davis Center for Mind and Brain. So the brain gets a series of snapshots of about a quarter-second, separated by brief gaps.
The working memory system smoothes out this jerky sequence of images by retaining memories from each snapshot so that they can be blended together. These memories typically last just a few seconds, Luck said.
"We use working memory hundreds of thousands of times each day without noticing it," Luck said. The system also seems to be linked to intelligence, he said.
Luck and postdoctoral researcher Weiwei Zhang wanted to test whether working memory stores a fixed, limited number of high-resolution images, or is a more fluid system that can store either a small number of high-resolution images or a large number of low-resolution images.
They showed volunteers a pattern of colored squares for a tenth of a second, and then asked them to recall the color of one of the squares by clicking on a color wheel. Sometimes the subjects would be completely unable to remember the color, and they just clicked at a random location on the color wheel. When subjects could remember the square, however, they usually clicked on a color that was quite close to the original color.
Zhang developed a technique for using these responses to quantify how many items a subject could store in memory and how precise those memories were.
"It's a trivial task, but it took us years to realize that we should use it," Luck said. The
|Contact: Andy Fell|
University of California - Davis