What Is the Capacity of Short-Term Memory?

J.M. Densing

Short-term memory is the first place that information is stored when it enters your brain, and it functions in a manner similar to a holding area. The capacity of short-term memory is between five and nine items, often referred to as "seven, plus or minus two." The items only remain there for about 30 seconds unless the person makes a conscious effort to retain them. The size of the pieces of information doesn't appear to make a difference, as each one could be as small as single letter, or as long as a whole phrase. If they are retained, the items are eventually transferred to long-term, or permanent, memory.

A grocery list containing more than 7 to 9 items may need to be written down due to the limits of short term memory.
A grocery list containing more than 7 to 9 items may need to be written down due to the limits of short term memory.

When information enters a person's brain, the first place it stops is the short-term memory, which has a very limited capacity. Only a few items can fit in short-term memory at a time, and they can't stay there for very long before they are either forgotten or stored in long-term memory. The generally accepted limit for the capacity of short-term memory is seven items on average. This number is based on the research of cognitive psychologist George A. Miller, who defined the capacity of short-term memory as seven items plus or minus two. He found that the majority of people could process about seven pieces of information at a time in short-term memory, with some people only able to handle five, and individuals at the upper levels retaining nine.

Alcohol intoxication may cause temporary, short-term memory loss.
Alcohol intoxication may cause temporary, short-term memory loss.

The limited capacity of short-term memory means that most people can only handle a small amount of information at one time. Without a conscious effort to remember, such as repetition of the information, the items will only be retained for about 30 seconds before they are forgotten. Each piece of information can be any size. For example, each digit of a phone number can be a separate item, or the whole phone number can be treated as a single chunk of information. Another example is that each piece of information could be a single letter of one word, the whole word could be treated as an item, or even an entire phrase.

Short-term memory may be utilized to remember a number looked up in a telephone book.
Short-term memory may be utilized to remember a number looked up in a telephone book.

One way to handle more information at one time is to organize it into chunks, such as remembering a phrase or a whole phone number. This can effectively increase the limits imposed by the capacity of short-term memory, helping a person fit a lot more information into that part of the brain because each item is bigger. New items tend to push out older ones, but if the person practices the information with repetition it can be retained instead of forgotten. Items that are retained and learned in this manner usually are transferred to long-term memory for permanent storage.

Short-term memory capacity can decrease with age.
Short-term memory capacity can decrease with age.

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Discussion Comments


@MrsPramm - Another trick I've heard is that you need to make sure you learn something three different ways within a certain amount of time (maybe it was three days, but I'm not sure) and that will ensure it goes from short-term to long term memory storage. So if you wanted to learn about a particular subject you could watch a documentary on it, read about it and discuss it with an expert and you should be able to memorize the facts without any extra effort.


@Fa5t3r - There are some tricks to improving your memory and most of them seem to try and short-cut information from the short term to the medium and long-term memory spaces. If you know a neighborhood really well, for example, you can use that to memorize numbers. When you hear each number, assign it to a particular building in the neighborhood in your mind. That pushes the numbers into the long-term storage area because you're associating them with information that is already in there.

It sounds like it wouldn't work, but there are people who can memorize the order of a shuffled pack of cards in just a few minutes by using tricks like this. So the average person should be able to use it to memorize a phone number.


I remember learning about this at university and thinking that it made so much sense, because I had noticed that sometimes I would be able to remember things that I hadn't consciously memorized, but only for a very short time after hearing them. Like a student who hears what the teacher is saying and manages to repeat it directly afterwards, but can't recall the information in ten minutes time.

It can actually be quite annoying when you want to memorize some numbers and it doesn't sink in because you get too much information at once.

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