Ever try to list a series of interesting things you’ve heard or own or read about for someone else, only to end up saying something like, “and…and…and I forget the other thing.”
There’s a good reason why we often “forget the other thing”–because our conscious mind, or what is sometimes called our “working memory,” has a limited capacity.
Just how limited has become clearer with new research published recently in the Proceedings of the National Academy of Sciences, described in a story by Clara Moskowitz at LiveScience.com.
How many things can you hold in your working memory? According to this new research, probably no more than three or four.
That’s lower than the previous estimate of seven, which was based on early research which might have contributed to the decision to make telephone numbers seven digits long. But it’s worth noting that telephone numbers are actually broken down into groups of three or four digits–one of those simple tricks we use when we need to remember more than three or four things at a time.
To get closer to the limit of working memory when you can’t use the grouping trick, the researchers at the University of Missouri-Columbia, led by psychologists Nelson Cowan, Jeff Rouder and Richard Mourey, first showed people arrays of different-colored squares. Then they showed them the same squares without the colors. After that, they were shown a single colored square in one location, and asked if that color was the color that was in that location in the original array.
The researchers had constructed a mathematical model based on the assumption that people have a fixed number of slots in working memory, each of which can only hold one item, and that when all these slots are filled, they start guessing at random.
Their model was able to forecast the results of the actual experiment with a high level of accuracy.
Not everyone has exactly the same limits to working memory, however: some have a bit more than others. People who have more slots in working memory seem to also learn, solve problems and comprehend what they read better.
Cowan believes that the correlation occurs because the more information you can hold in your mind at any one time, the more information you can interrelate.
It is possible to improve performance on some working-memory-dependent tasks with training. Children who practice these tasks get better with time–and as their scores on memory tasks improve, their scores on other tests that measure attention and reasoning also improve.
And some people can pull of amazing feats of memory. There’s actually something called the World Memory Championships, held most recently in Bahrain in September of 2007. Competitors there were able to recall hundreds of digits in order after only five minutes of study.
But that doesn’t mean their working memory has hundreds more “slots” than those of us ordinary mortals.
Moskowitz quotes Michael Kane, a psychologist at the University of North Carolina at Greensboro (who wasn’t involved in the new study): “A very famous study was a test done of a long-distance runner who learned to associate digits together in ways that were meaningful to him with respect to running times,” Kane said. “He could repeat back lists of up to 80 digits in the right order, but if you gave him a list of words, he was at seven plus-or-minus two like everyone else.”
Does working memory correlate somehow to long-term memory? According to Moskowitz, researchers are still divided on that question. Some think the two kinds of memory are completely separate, while others believe working memory is simply the part of long-term memory we can currently access.
Even more interestingly, many researchers believe that almost everything we experience is encoded into long-term memory, and that when we forget something, it’s not that it’s vanished from our mind: rather, we’ve simply lost access to it.
Which raises the intriguing possibility that we might someday figure out a way to improve that access–making forgetting will a thing of the past.
Whether that’s a good thing or not, of course, may well depend on what you have to remember.
1 comments
Working memory, long-term memory… You mean we’ve got RAM and hard disk space? Oy.
So Sherlock Holmes didn’t have it quite right then.