Short Term (Working) Memory:
Short term memory is also roughly synonymous with "working memory" or conscious thought. As I am typing this, the information is flowing into and out of my working memory. When you are talking or answering questions on an exam, the information must be brought into working memory for you to manipulate, and your words and answers come out of working memory. As you try to understand the words on this page, your ability to understand these concepts depends on your working memory (and to some extent your long term memory).
Despite its central importance in the memory process, short term memory is in many respects the "bottle-neck" of the memory process. It is very limited in terms of the both its capacity (amount of information it can hold) and its duration (length of time it can hold information).
Let us start by considering the duration of memories in short term memory. The duration of short term memory is 15 -30 seconds (usually closer to 15 than to 30 seconds).
Imagine that you are asked to remember a telephone number that is new to you. You could probably keep in in your memory for more than 30 seconds, but only by saying it over and over again "in your head." This is called "rote rehearsal" or "maintenance rehearsal." Rote rehearsal or maintenance rehearsal can help you to keep information in short term memory for more than 30 seconds. BUT, if anything happens to interrupt your rote rehearsal, the information will be lost unless you have already succeeded in moving the information into long term memory. You can probably think of real life examples where this has happened: you were trying to keep a telephone number in your head, but someone interrupted your thoughts, and you lost the number forever.
Many students are in the habit of studying by reading things over and over again, a form of rote rehearsal. However, if the exam is more than a few minutes away, and if you are anticipating any interruptions prior to the exam, this is probably NOT a very good strategy. If you get interrupted, and the information has not made its way to long term memory, it will be lost. If you want to remember information for an exam some time in the future, or so you can use it in real life, the information has to make it into long term memory, and it has to get there in such a way that you can get it back out when you need it.
Look again at the drawing of the Three-Box Model of Memory. Notice that there is only a dotted line from working memory to long term memory when rote memorization is used. That is because rote memorization is NOT very efficient in moving information to long term memory. (Elaborative rehearsal is a better strategy that we will cover later.)
Important point: Rote memorization can help to keep information in working memory, but it is NOT an efficient way to move information to long term memory.Let us move on to a consideration of the capacity of short term memory. If I gave you a series of letters to remember (e.g., twpbdrt), your ability to remember the series correctly would probably depend on the number of letters in the series. Most people can remember a series of letters correctly if there are only 3 or 5 letters in the series. About half the people asked to remember a seven-letter series have difficulty. Relatively few people can remember series consisting of 9 or 11 letters correctly. This finding, that the limit on short term emoryory is around 7 items, is one of the most consistent findings in all of psychology. George Miller, a very famous cognitive psychologist, coined the phrase "the magical number seven, plus or minus two," to describe the capacity of working memory. (You can read this classic paper at http://psychclassics.yorku.ca/Miller/ .)
Point: The capacity of short term (working) memory is seven, plus or minus two.Are you feeling skeptical at this point? I hope so! I have told you two things that are inconsistent. First I told you that we essentially "think" out of our working memory, and that I am writing this out of my working memory. Second, I told you that the capacity of working memory is seven plus or minus two items. If the limit on working memory was literally 7 letters, I could not write my own name, which is Barbara Brown, much less form a complete sentence. It is true that short term memory has a capacity of 7 somethings, but the limit is not necessarily 7 letters.
To understand the real limits of short term (working) memory, try the following. Read the string of 15 letters below, then close your eyes and try to repeat them back in the correct order.
BGI TAE LTE GDO HTE
Most people cannot do this. There are 15 letters, and this exceeds the capacity of working memory by quite a lot. However, if we rearrange the letters, this same task can seem easy. Try it again!
THE EAT DOG BIG LET
Even though there are still 15 letters, most people will get all 15 this time. Why were the letters easier to remember this time?
When the letters are arranged to form words, they are easier to remember. Each word is one unit of meaning. With the first set of 15 letters, each letter was the unit of meaning, so there were 15 units to remember. With the second set of 15 letters, each word was a unit of meaning, so there were only 5 units to remember.
If the words are arranged in order to form a sentence, they are even easier to remember, as the sentence itself becomes a unit of meaning:
LET THE BIG DOG EAT
(This sentence is supposed to be meaningful to Georgia fans, although I am told that I misspelled "dawg.")
The capacity of short term memory is approximately 7 "chunks."
A CHUNK is a meaningful unit of information.We can increase the absolute capacity of short term memory by combining bits of information into meaningful units, or chunks. This process is called "chunking."
Instructors try to help you chunk information by focusing on the ways that the pieces of information to be learned relate to one another. Students working on their own often try to memorize long lists of terms without understanding how these pieces of information relate to one another; they quickly overwhelm the capacity of short term memory, and their attempts at learning are ineffective. Whether or not your instructor helps you, always try to understand how the pieces of information you are trying to learn relate to one another and to other information you already know.
Important point: To make your learning more effective, practice "chunking" and try not to work with more than seven chunks at a time.This page was last revised on 09/09/2008.