Short-Term Memory (abbreviated STM, also known as "Working Memory")

Short-term memory is small. To emphasize STM's limited capacity to hold information, STM is often compared to other objects that have limited capacity: small buckets, small funnels, and small sponges. Because STM is so limited, STM is often referred to as "the bottle neck of the memory system."

Examples illustrating that STM is  small


How small is STM?

Implications of STM being so small

Short-term memory is short (it typically lasts about 20 seconds)

The reason information stays in STM for such a limited time seems to be due to the limited size of our STM combined with our limited attention span. Some evidence:

Short term memory (also called working memory) is your conscious mind

Although there are many aspects to STM, in this page, for simplicity's sake, we will focus on  two of STM's roles:
(1) holding information in consciousness and
(2) being the narrow, shaky bridge through which information goes in and out of  LTM.

Because working memory is limited (it holds, at most, 5-9 chunks [chunks are groups of items]), our thinking and our attention are limited. Specifically,

  1. We can only pay attention to a few things at a time, so multi-tasking can't work.
  2. Examples showing that we can only pay attention to a few things at a time: Analogies to help you understand that we can't multi-task:
  3. Teachers and presenters may overwhelm their audience's STM by going too fast or by presenting too much information on a PowerPoint slide.
  4. The complexity of the world can't fit in STM, so we oversimplify the world, leading to not seeing differences between people, to stereotyping, and to seeing things in terms of absolutes (i.e., seeing things in terms of black and white rather than in terms of shades of gray).

What is chunking and how does it allow us to keep more information in STM?

The way to get around the limits short-term memory's limited size puts on us is to chunk: group several different individual bits into one unit.  For example, U.S. citizens could group the twelve numbers "177  614  922  02  4"  into three chunks:
1776     1492     2024.

In the "1776, 1492, 2024" example, you grouped (re-grouped?) the information into chunks by connecting the presented information to organized units of information that you already had stored in your permanent memory. Specifically, instead of having to remember 12 numbers, you just had to "point" to 3 chunks of information you had stored in your permanent memory. If you can't connect new information to units you already have stored in permanent memory, you will not be able to chunk that information until you create those units (so, for Americans, "FBI" is one chunk, but "BFI" probably is not). You can create a new unit by cementing together isolated information bits and then storing those connected bits as one unit in your permanent memory. For example, you could link together the many individual words that define "iconic memory" and then store those words in your permanent memory as a single unit.  After you have done that, you will be able to hold the entire definition of that term as a single chunk in STM  by "pointing" to the place in your permanent memory where you have that definition stored. Note that when you first encountered iconic memory's definition, it was "too big" for your STM, but now--or soon--it will only take up one chunk of your STM's 5-9 chunk capacity.  So, once you learn a psychological term, you increase your ability to chunk psychological information.

Visual analogies illustrating that chunking makes it easier to keep more information in STM:

But why chunk information? (Why are big chunks better?)

Chunking, by allowing us to keep more information in STM, lets us think smarter.

To see the power of chunking, consider experts. Experts have formed large chunks of information related to their field. As a result, they can hold a large amount of that information in their head while still having room in their working memory to think about that information. So, when thinking about their field, they can think about many things at once (e.g., chess experts, physicians, and football coaches can quickly absorb much more information about their fields than the average person can when the experts can chunk that information). Note, however, that if experts are thinking about things outside of their field--where they can't chunk as well--their thinking is much more limited (one of many reasons why supposedly smart people do stupid things).

Some chunks that you may have learned that have made you more expert:

Since students who chunk information when studying get better grades in college (Gurung, 2005), you might wonder how to chunk information so that you could get better grades. One way is to study terms until each term's definition takes up only a single chunk in memory. In addition, you could turn the many terms you have to learn into a smaller number of groups of terms by

STM Myth STM  Fact
Short term memory lasts an hour or maybe even a couple of days. Short term memory lasts about 20 seconds.
Short term memory can hold 5 to 9 items. Short term memory can hold 5 to 9 chunks.
Short-term memory is big enough that people can multi-task effectively.  Because of STM's limitations, people are terrible at multi-tasking.
If information is in STM long enough, it will automatically move into permanent memory. Maintaining information in STM  for a long time does not necessarily move that information to permanent memory.

Review STM

Learn more about STM: To get a better understanding of what short-term memory is and how understanding short-term memory can help you think and learn better, read Scott Young's article on working memory (long, but useful!).

Reflect on STM's importance

Realize that STM, as the narrow bottle neck of the memory system, not only puts limits on how much information you can put into LTM at one time (so professors shouldn't speak to quickly or put too much information on a PowerPoint slide) but also limits how much information you can get out of LTM at one time (click to see visual analogy).  At one level, you know that STM limits how much information from LTM that you can bring up at once: You wouldn't ask your partner to name 20 things they love about you (unless you wanted to be depressed)--and you would certainly hope that a professor wouldn't call on you to name 10 important psychological discoveries. However, you may not have realized that, because all your relevant knowledge about a situation will sometimes be too big for STM to hold, all your relevant knowledge can't always come to mind when you  need it. As a result, you will make mistakes even though you knew--or at least your LTM knew--better.  Note that if you are distracted, preoccupied, emotional, sleep-deprived, or otherwise impaired, you will have less room in STM for information from LTM and thus will be even more likely to make mistakes due to not using what you know.

As you have seen, STM's limitations limit not only what you can keep in STM but also both what you can upload to LTM and what you can download from LTM. How can you get around these limits of STM? One way is to offload information from your STM to your phone, to a small notepad, or to a 3 X 5 index card. Another approach is to chunk information.

Without chunking, almost everyone can hold between 5 and 9 items in short-term memory. So, when President Trump was given a test in which he had to repeat five words, failing on that task would have been very bad. Succeeding on the task, however, was not terribly impressive. To judge the difficulty of that test, you can see it here.

President Trump implied that he did not use a strategy for remembering the 5 words: "Person, Woman, Man, Camera, TV." Instead, he attributed his ability to recall of those words to having a great memory. President Trump could have made it easier on himself  by chunking the 5 individual words into one or two chunks. If you had to remember "Person, Woman, Man, Camera, TV," how would you turn those 5 items into one or two chunks?

Most of the questions on the test that President Trump took involved memory. Some of the questions tested short-term memory; other questions (e.g., testing whether he could identify the animal in a picture as an elephant) tested long-term memory. As you can imagine, if someone did poorly on that test, their mind would be very limited. Indeed, such a test might be used to determine whether a person could live on their own. So, both short-term and long-term memory are important to living a full life. We have discussed short-term memory. We will now turn to long-term memory.

On to Long Term Memory

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