Short-term memory
Short-term memory holds a small amount of information for a short time, about 15 to 30 seconds if you do not repeat it. It fits only a few items at once, classically 7 plus or minus 2, and closer to 4 chunks by newer estimates. Anything you want to keep has to move on to long-term memory.
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In more detail
In the classic multi-store model from Atkinson and Shiffrin (1968), information flows through three stages. Sensory memory catches everything for a split second. What you pay attention to enters short-term memory. What you process well there gets stored in long-term memory. Short-term memory is the narrow middle of that funnel.
Two limits define it. Duration: in a famous 1959 experiment, people forgot most of a three-letter string within about 18 seconds when they were kept from repeating it. Capacity: George Miller wrote in 1956 about the magical number seven, plus or minus two. Later work by Nelson Cowan put the real limit nearer 4 chunks once you stop people from grouping items.
Short-term memory is often confused with working memory. Short-term memory is the storage part, holding items for a moment. Working memory is the active part, holding and using them at the same time, like doing mental math. For studying, both limits mean the same thing: rereading a page loads short-term memory and then it drains away. Only retrieval, linking ideas and spaced review get it into long-term memory.
The three memory stores
| Sensory memory | Short-term memory | Long-term memory | |
|---|---|---|---|
| How long | Under 1 to about 3 seconds | About 15 to 30 seconds without rehearsal | Minutes to a lifetime |
| How much | Large, raw sensory input | About 4 chunks (classically 7 plus or minus 2) | No known limit |
| Gets in by | Your senses, automatically | Paying attention | Processing meaning, retrieval, repetition over time |
| Lost by | Fading almost at once | Fading or being pushed out by new items | Interference, weak cues, disuse |
Example
A professor puts a 10-step derivation on one slide and talks over it. By step 6, Mia has lost step 2. Her short-term memory is full. Next time she writes the steps in three groups with a label for each, and afterwards quizzes herself on the groups from memory. The chunks fit, and the quiz moves them into long-term memory.
How to use it
- 1
Group information into chunks, like 3 to 4 steps under one label instead of 10 loose items.
- 2
Take in less at once. Pause the lecture or close the page after each idea.
- 3
Write things down instead of juggling them in your head while you work.
- 4
Within a minute, say the idea back in your own words, then test yourself again later that day.
- 5
Review over several days so the item moves from short-term into long-term memory.
How StudyPDF does this
Upload your lectures and StudyPDF splits them into topics and concepts, so you study a few ideas at a time instead of a whole chapter at once. Flashcards and quizzes then make you pull those ideas back out, and per-concept mastery shows which ones made it into long-term memory and which ones faded.
Sources
See also
Common questions
How long does short-term memory last?
About 15 to 30 seconds if you do not rehearse the information. In the classic Peterson and Peterson study from 1959, people who were blocked from repeating a few letters forgot most of them within about 18 seconds. Repeating the item keeps it active longer, but it still does not store it for the long run.
What is the difference between short-term memory and working memory?
Short-term memory is the storage part. It holds a few items for a few seconds. Working memory is the active system that holds information and works with it at the same time, like solving a math problem in your head. Many textbooks treat short-term memory as the storage part of working memory.
Put it to work on your own course
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