University of Iowa News Release
Dec. 9, 2003
UI Researchers Find Adult-Like Short Term Memory In Infants By Age 1
New research from the University of Iowa shows that infants' visual short-term memory -- a key element of brain development -- expands significantly in the second half of the first year of life, reaching adult capacity by 12 months.
Shannon Ross-Sheehy, Lisa M. Oakes and Steven J. Luck, all of the psychology department in the UI College of Liberal Arts and Sciences, conducted a series of tests to determine how many objects infants could hold in short-term memory at different ages between six and 12 months. Their results, published in the November/December issue of the journal "Child Development," are the first to demonstrate conclusively that infants have visual short-term memory and that its capacity is similar to that of an adult by the time babies reach their first birthdays.
Visual short-term memory is crucial for infants trying to learn about the world around them, Oakes said. Before they can start comparing objects to learn what makes them similar and different, infants must be able to remember an object they have seen before but are not currently looking at.
"For example, an infant who is trying to learn the difference between dogs and cats may rarely see a dog and a cat right next to each other," she said. "So the infant will need to compare a memory for the shape of a cat seen at one moment with the shape of a dog seen a few moments later."
To test infants' visual short-term memory, the UI team showed infants two computer monitors at the same time, each displaying a set of one to six colored squares that flashed on and off. On one monitor, the colors remained the same at each flash. On the other monitor, one item changed color each time the squares flashed on.
The team expected the infants to watch the changing side longer than they would watch the unchanging side, since infants generally look longer at things that change than at things that remain constant. Oakes noted that this preference for change depended on the infants being able to remember the colors between the time they flashed off and flashed on again. Because of this the team predicted that infants' preference for the changing side would decrease when the number of items on the screen exceeded the number of items they could store in short-term memory.
Infants six months and younger preferred the changing side only when it contained a single colored square, indicating that these young infants stored only one object in short-term memory. By the age of 10 months, infants looked longer at the changing side when it contained one to four objects, but did not prefer the changing side when it contained more than four objects. This indicated that the older infants had a short-term memory capacity of four objects, which is similar to adult memory capacity.
Oakes cautions that this does not mean infants have fully developed short-term memory by 12 months. Previous studies have shown that adults can remember multiple features of up to four objects, but these infants were only tested for their recognition and memory of a single feature-color. The team plans further studies to determine whether infants visual short-term memory is developed enough to remember multiple features, such as shape and size in addition to color.
STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.