What is the primary characteristic of short-term memory?

Short-term memory is primarily defined by its limited capacity and the brief duration for which it holds information. This type of memory is typically capable of storing approximately seven items, plus or minus two, at any one time. Unlike long-term memory, which can retain information over extended periods, short-term memory tends to only retain information for a duration ranging from about 15 to 30 seconds unless actively rehearsed. This characteristic is essential for many cognitive tasks, such as problem-solving or following a conversation, where immediate recall of information is necessary.

The other options describe characteristics that do not align with the nature of short-term memory. For example, the idea of holding unlimited information for long periods better characterizes long-term memory, while the suggestion of only processing sensory information pertains more to sensory memory. Similarly, the concept of storing memories without any time limit is also indicative of long-term memory rather than short-term memory, which is inherently transient. Thus, the correct understanding of short-term memory's limited capacity and duration is key to grasping its role in our cognitive processes.