The Limits of Memory: We Can Only Remember Four Things at a Time
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April 29, 2008

The Limits of Memory: We Can Only Remember Four Things at a Time

Kingscollegepinkfull_2_2 New research in to our minds capabilities to retain knowledge has shed light on a question that has been discussed for many years; how much, can our mind remember, at a time?

The study focused on ‘working memory’, that part of our mind which refers to the temporary storage of information that still allows us to pay attention and manipulate it. Some believe that working memory is separate to any of our other memory storages, many believe that working memory is simply that part of our long-term memory that we can currently access.

Research originally suggested that our working memory cut off point was around the seven items mark. However scientists are revising that idea, when adding the limitation of no memory tricks, such as repeating items over and over or grouping them together.

Telephone numbers are a good way of looking at what scientists are referring to here. For example, Microsoft’s Corporate HQ telephone number is 800 642 7676. At first blush, remembering that number would suggest the ability to remember 7 or more items. However considering the blocking – 800 + 642 + 7676 – and the repetitive nature of the number, one cannot be so certain.

"For example, when we present phone numbers, we present them in groups of three and four, which helps us to remember the list," said University of Missouri-Columbia psychologist Nelson Cowan, who co-led the study with colleagues Jeff Rouder and Richard Morey. "That inflates the estimate. We believe we're approaching the estimate that you get when you cannot group. There is some controversy over what the real limit is, but more and more I've found people are accepting this kind of limit."

The study had to take a new method in testing this revised theory, given the problems presented with numbers or letters. Thus, subjects in the study were presented with an array of different colored squares. The subjects were then shown an array of the same squares, but this time without the colors. Finally, they were shown a single colored square in one location, and asked whether the color matched that of the square in the same position at the beginning of the test.

"What's nice about this visual task that they used is that it really makes it difficult to use some of those common strategies that are helpful with verbal lists," said Michael Kane, a psychologist at the University of North Carolina at Greensboro, who was not involved in the new study. "I think Cowan's work has really been convincing in this."

This new method does build upon previous research, but it allows for the most rigorous mathematical test of the three-to-four memory ability.

Backing up the revised testing method was a computer model, programmed to assume that humans have a fixed number of memory slots in their working memory bank. Programmed to believe that each slot could only contain one piece of information, when the slots were filled, the model predicted that people would begin making random guesses. Subsequently, the model was able to predict with a surprising level of accuracy the results of the trials.

"It is a pretty simple mathematical model but it predicted a very exquisite pattern of data," Cowan said, speaking to LiveScience. "The results really were simple. With a single value of working memory capacity we could really account for all those different scenarios."

Naturally, there is a variation amongst some individuals, but the average cap does seem to hover around the 3 or 4 memory slot mark. Interestingly though, those individuals that have a higher level of working memory often do well at learning, reading comprehension and problem solving.

"People accept that intelligence seems to be related to working memory," Cowan said. "The information you can hold in your mind at one time is the information you can interrelate. If you have a better working memory we believe that your problem-solving abilities are better."

Posted by Josh Hill.

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http://www.livescience.com/health/080428-working-memory.html

Comments

4 wifes at a time.

There's an obvious problem with an experiment designed around coloured squares - above a certain number, it requires multiple eye movements during the training period just to take in, let alone remember. That's what always does for me in the "memory' rounds of certain popular TV shows.

However, a simple litmus test of whether "four items" is correct or not might be whether it is possible to sight read a five-part fugue. It is possible to do this, suggesting straight away that "four items" is incorrect.

It's amazing how many "professional" scientists miss even the most basic things in the design of their experiments, isn't it? And how many of those sloppy scientists you end up eulogising over.....

So, if you have some training, you can remember alot. When in high school, i'd studied the Japanese Abacus. After about three months, the book said i should try mental arithmetic. I tried it. After a few days of exercises, i was doing things like "divide 105,198 by 534". Is that 9 things? But it was easy, tried dividing pairs of 9 digit numbers, getting 9 significant digits of answer, then verifying with a calculator. That was easy, so i tried computing the sin(27.3 degrees) using Taylor series expansion, to ten significant digits. I later determined that i must have needed about 80 digits of intermediate results. Things like x^2 (where x is 27.3 degrees converted to radians) and 17! I'd gotten the right answer, so i must have remembered all that stuff.

It took more than a month to learn 11 digits of pi, in the same era.

Unfortunately, i did not continue practicing, so can't do it anymore.

There is another way of looking at this. We carry 10 to 12 seconds of 'buffer' capacity in our brain which lets us nderstand speech and enjoy music and read text with ease. If this 'buffer' was not available, we would not be able to connect one word to the next and a set of words to the next to understand what is being said or written. The
continuity of music would be lost on us.

I call this the 'resident time' in our head. In all literature, no sentence is longer than 5 or 6 seconds of normal reading time. If sentences were very long they are difficult to understand.

Likewise, when we speak, we always pause once every two or three seconds. Like the commas in this sentence. If someone speaks without a pause for say, 30 seconds, I don't think we can
understand much of what's said.

(Just read the above para continously ignoring the commas and the periods to see what it
sounds like!)

Animals (and children under five) do not have this buffer time, that's why they can comprehend
only a word or two at a time.

Children develop this buffer by listening to and reading stories.

Intelligence is directly related to this time-span.

Therefore, is it really "memory" we are talking about in the above article - or what is termed as "working memory" is actually the "resident time span" developed by an individual?

Let me add that the short-term memory is the system where the individual manages the information from which it is interacting with the environment. Great article.

who wrote this?


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