What is short-term memory?

Definition

Short-term memory is the cognitive system that holds a small amount of information for a few seconds, typically in the range of 15 to 30 seconds without rehearsal. It sits between sensory memory (which holds raw perceptual input for under a second) and long-term memory (which can hold information for years).

Short-term memory is often used loosely to mean working memory, but the strict distinction is useful. Short-term memory is the passive storage layer; working memory is the active manipulation layer that includes short-term storage. When researchers say "short-term memory" they usually mean the storage component specifically.

Capacity is small. The classical Miller (1956) figure is seven items, plus or minus two; later research has refined this down closer to four chunks for arbitrary unrelated items. Capacity grows substantially when items can be grouped into meaningful chunks (a familiar phrase counts as one chunk; a string of random letters of the same length counts as many).

Why it matters

Short-term memory is the gateway to long-term memory. Information that is not held in short-term memory long enough to be encoded does not make it to long-term storage. Most "I am so forgetful" complaints in everyday life are actually short-term memory failures rather than long-term memory failures: the information was never properly captured in the first place.

Short-term memory is also extremely sensitive to interference, fatigue, and attention. The reason you cannot remember the four things you walked into the kitchen for is rarely that the storage was overloaded; it is usually that something interrupted attention during the few seconds between intent and arrival.

How it works in the brain

Information enters short-term memory after passing through sensory memory and being attended to. Once there, it decays over a window of roughly 15 to 30 seconds unless rehearsed (e.g. saying a phone number to yourself repeatedly) or transferred to long-term memory through encoding.

The neural substrate involves prefrontal cortex (for the active maintenance) and content-specific posterior regions (auditory cortex for verbal information, visual cortex for visual). Working memory training generalises the most reliably within the type of content trained, suggesting the storage subsystems are at least partly distinct.

How to improve short-term memory

The most powerful "improvement" is technique rather than capacity. Chunking (grouping individual items into meaningful units) effectively expands what you can hold without changing the underlying storage. So does deliberate rehearsal, paying conscious attention, and reducing interruptions during the short window between perception and storage.

Training on specific span tasks (Corsi blocks, complex span) produces measurable gains on those tasks. Whether that transfers broadly to everyday short-term memory is contested, with the Simons et al. (2016) review concluding the transfer is narrow.

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Frequently asked questions

Related terms

• Miller (1956), "The Magical Number Seven, Plus or Minus Two"
• Cowan (2001), "The magical number 4 in short-term memory: a reconsideration of mental storage capacity"
• Baddeley & Hitch (1974), "Working Memory"
• Simons et al. (2016), "Do Brain-Training Programs Work?", Psychological Science in the Public Interest