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Tuesday, October 26, 2021

UCD Psychologists test memory’s precision

Researchers at UC Davis recently published a study on the short-term “working memory.” Professor of psychology Steven Luck and postdoctoral researcher Weiwei Zhang at the UC Davis Center for Mind and Brain found that adults store a limited number of high resolution images in the “working memory.”

The brain uses working memory to piece together sensory information and store it. Instead of storing many fuzzy images, Luck and Zhang found that the working memory stores a fixed number of high resolution images for a few seconds.

“The capacity of working memory is so limited, you have to be careful what is stored in working memory,” Luck said.

They found that this system of limited storage cuts down on useless information, or visual “noise.” Easily compared to a digital camera, the “working memory” uses up valuable space when saving these high resolution images, but unlike a camera, the visual memory cannot be set to save a greater number of fuzzier images.

Zhang designed the experiment used to test the working memory of adults. The researchers showed subjects a pattern of colored squares for one-tenth of a second. The subjects were then asked to click the colors of the squares by clicking on areas of a color wheel. The accuracy of the colors showed the precision of the test subject’s working memory.

“High resolution would mean how precise the colors are,” Zhang said.

Luck and Zhang worked with UC Davis psychology professor Lisa Oakes, who tested the working memories of infants. Oakes compared the space for high resolution images as a limited number of “slots,” and she wanted to know whether infants have the same system of slots.

“We are trying to understand what kind of working memory babies have,” Oakes said.

In one test, Oakes showed infants movies of objects changing and movies where the objects stayed the same. Oakes said that if there is a reaction to a change in environment, this shows the presence of a working memory.

As an example, Oakes said if a baby is looking at its mother as the mother smiles, but then the baby closes its eyes and mother is frowning when the baby looks back, a reaction in the baby proves that the previous smile was stored in the working memory.

Though the infants could not offer the same feedback as adults by talking or clicking a screen, Oakes used the infants’ eye movements to track their reactions.

“With infants, we rely on how long they look at things,” Oakes said.

Another test had infants look at a colored square briefly and then look at another square that sometimes was a different color. Oakes found that the infants looked at the squares longer when they were different from the previous color.

“Babies, like adults, can remember the colors of objects,” Oakes said.

That the infants noticed the difference between the two squares shows that information is stored in our working memory early in life.

Oakes also found that the precision of working memory increased noticeably between six and 10 months old. At six months old, most infants could only remember the color of one square they were shown, but between 10 and 12 months old, they would remember two to three squares. Adults tested could recall three or four squares.

Not everyone has the same level resolution in the working memory. Luck and Zhang found that people who could save more in the working memory had a better ability to solve new problems and keep track of objects out of view, an ability called “fluid intelligence.” Working memory is also used for processes like adding a string of numbers.

The research was conducted three years ago at the University of Iowa – before either researcher came to UC Davis – and the paper was published online in the journal Nature on Apr. 2. Grants from The National Institute of Mental Health supported the research.

Luck and Zhang will soon test the system of working memory in subjects with schizophrenia.

 

MADELINE McCURRY SCHMIDT can be reached at campus@californiaaggie.com.XXX

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