How many items can you hold in your short-term memory (STM)? Most people can remember about 7 items for about 15–20 seconds. With rehearsal—mentally repeating items — you can increase the time that items stay in STM. And with chunking — combining individual items into larger chunks — you can increase the number of items.
The Magical Number Seven: Limited Capacity of STM
How much can people hold in short-term memory? The best estimate seems to be about 7 unrelated items, as George Miller noted in 1956, when he published a famous paper, "The Magical Number Seven, Plus or Minus Two." Although the actual number of items a typical adult can hold in STM ranges from 5 to 9, for most people and for most tasks, things become unpredictable after about 7 unrelated items. That's when items tend to get lost or "drop out."
STM Limit: 7 Unrelated Items
When we say the capacity of STM is 7 items, it's important to note that this does not mean STM can store only 7 numbers or 7 letters. STM can hold dozens of numbers or letters if they are combined through chunking into larger meaningful units such as telephone numbers, words, phrases, or sentences.
Short-term memory (STM) is where you keep nonsensory information for a short time. The time limit of STM is generally around 15-20 seconds. For example, if someone introduces you to five or six people consecutively, you might have forgotten the names of the first one or two by the time you get to the fifth or sixth.The size limit of STM is generally around seven unrelated items. For example, if you overhear someone say a nonsensical ten-word magic phrase that guarantees happiness, you probably won’t be able to remember it! Rehearsal — mentally repeating items — can extend the time limit on STM, because each time you repeat an item, you start the STM clock over again at zero. The size limit on STM can be extended by chunking — combining individual items into chunks that can be remembered as a whole. For example, if the ten word magic phrase consisted of five two-word chunks — sleep-wake cat-dog first-last land-sea up-down—you might find it much easier to recall.
Diana was trying to call a friend who worked at the Freud Museum in Vienna, Austria, but she needed to get the number from a telephone operator. Diana didn't have a pen and paper, so she tried to memorize the number as the operator read the digits: "4-3-1-3-1-9-1-5-9-6." Unfortunately, she forgot the number before she was able to make the call.