Because of the limited capacities of STM, we cannot store everything. The brain has a finite capacity to store information – Miller’s magical seven items. Information about objects must be stored in sensory memory (short-term memory) until they are processed. When processing occurs, then information is transferred back into the working memory.
Miller also discovered that capacity of STM can extend by grouping related items into ‘chunks.’ For example, if we assume STM has 7 ports, then a list of over 7 items overloads the system; however, if a string of letters has an identifiable sequence or forms a recognizable word, our STM can deal effectively with it as a single item, allowing additional items to pass through without interference. Similarly, the 14 digit number 11235813213455 isn’t very memorable, but once we recognize it as the first 10 digits of the Fibonacci Sequence (1, 2, 3, 5, 8, 13, 21, 34, 55), we treat it as a single chunk.