Sensory and short-term memory
Also known as: short-term memory, sensory memory, working memory
Sensory memory is the fleeting, high-capacity register that holds raw sensory input for a fraction of a second to a few seconds; short-term memory holds a limited amount of attended information — about 7 ± 2 items — for roughly 15 to 30 seconds without rehearsal.
Sensory and short-term memory are the first two stages of the classic Atkinson-Shiffrin (multi-store) model of memory, which describes information flowing from sensory memory to short-term memory and, with sufficient processing, into long-term storage.
Sensory memory is an extremely brief, high-capacity buffer that holds raw sensory input just long enough for the brain to decide what deserves attention. Iconic (visual) memory lasts only a few tenths of a second, while echoic (auditory) memory persists for a few seconds — which is why you can "replay" the last words someone said even if you weren't listening closely. Information that is not attended to decays immediately.
Information you attend to enters short-term memory (STM), which holds roughly 7 ± 2 items (Miller's magic number; more recent estimates suggest about 4 chunks) for approximately 15–30 seconds without rehearsal. Capacity can be stretched by chunking — grouping digits into a phone-number pattern, for instance — and duration extended by maintenance rehearsal. The related concept of working memory, developed by Baddeley, treats this stage as an active workspace with a phonological loop, visuospatial sketchpad, and central executive that manipulate information rather than merely storing it.
The MCAT tests sensory and short-term memory within its memory and cognition content — iconic versus echoic stores, capacity and duration limits, chunking, and working memory components — and AP Psychology covers the same material in its cognition unit on encoding, storing, and retrieving memories.
Key takeaways
- Sensory memory holds raw input very briefly: iconic (visual) for under a second, echoic (auditory) for a few seconds.
- Short-term memory holds about 7 ± 2 items for roughly 15–30 seconds without rehearsal.
- Chunking increases effective STM capacity; rehearsal extends its duration.
- Working memory reframes STM as an active workspace with a central executive, phonological loop, and visuospatial sketchpad.
- The MCAT and AP Psychology both test the multi-store model and its capacity and duration figures.