What characteristic defines working (short-term) memory?

The defining characteristic of working memory is that it can typically hold five to nine items at a time. This principle is often associated with George A. Miller's research, which established that the average capacity of working memory is about seven items. This limited capacity enables individuals to manage and manipulate a small amount of information actively while engaging in tasks such as problem-solving, reasoning, and comprehension.

Options that suggest unlimited storage or extended duration contradict the empirical understanding of how working memory functions. Additionally, the notion that information is stored solely in a visual format is inaccurate, as working memory can process information in various formats, including auditory and verbal. This versatility allows it to function effectively in different cognitive tasks requiring attention and memory.