Short-term memory (STM)—often used interchangeably with working memory—acts as the brain's scratchpad, holding a limited amount of information for immediate use. Without rehearsal, these contents fade within 15–30 seconds.
What Gets Stored
- Sensory Inputs: Brief retention of visual (iconic), auditory (echoic), and tactile impressions that feed into STM.
- New Learning: Phone numbers just heard, names from introductions, instructions received moments ago.
- Active Manipulation: Information being mentally juggled—calculating a tip, following multi-step directions, reasoning through a problem.
- Emotionally Tagged Events: Salient moments (fear, joy, surprise) get priority encoding into long-term memory.
Defining Characteristics
- Capacity: Classic research suggests 7 ± 2 items (Miller), though modern work favors 4 ± 1 meaningful "chunks" (Cowan).
- Duration: Roughly 15–30 seconds without active rehearsal.
- Encoding: Primarily acoustic; semantic (meaning-based) encoding aids transfer to long-term storage.
- Fragility: Easily disrupted by distraction, interference, or time pressure.
Clinical Relevance
STM deficits appear in ADHD, traumatic brain injury, early dementia, delirium, and anxiety disorders. Standard assessments include digit span, Corsi block-tapping, and n-back tasks—tools that probe both storage and manipulation capacity.
