A telephone number heard once can be repeated immediately but vanishes if attention shifts. Short-term memory is the capacity to hold a small amount of information in an active, readily available state for a brief period.

Classic estimates placed the span at roughly seven items, later refined to fewer when material is complex. Information decays within seconds unless rehearsed or transferred to longer-term storage. Short-term memory is closely related to, and sometimes subsumed by, the broader concept of working memory, which emphasizes manipulation as well as storage.

Interference and limited capacity are its defining constraints. Chunking increases effective capacity by grouping elements into meaningful units. Short-term memory supports comprehension, problem solving, and the moment-to-moment continuity of thought. When it fails, even simple tasks become fragmented.

The present moment of cognition depends on what short-term memory can maintain.