What is short-term memory?

Short-term memory (STM) is the capability of holding information in mind in active, readily available state for a short period of time. The duration of short-term memory is in the order of seconds.

 

 

Duration of short-term memory

The contents in STM spontaneously decay over time. Thus to retain information for longer time, the information must be periodically repeated or rehearsed.

 

Capacity of Short Term Memory

Experiments have shown that STM has a limited capacity to remember 7+/-2 chunks of information at a time. This limit is called memory span. In a memory span test, the experimenter presents lists of items (e.g. digits or words) of increasing length. An individual span is determined as the longest list length that he or she can recall in the given order for at least half of the times.

 

Chunking

Chunking is a process by which you can expand your ability to remember things in STM. Chunking means organizing information into meaningful groups. Average person can retain only about four different chunks(units) in short-term memory at a time. Effective chunking can greatly increase a persons recall capacity. For example, in recalling a phone number, the person could chunk the digits into three groups: first, the area code (such as 215), then a three-digit chunk (123) and lastly a four-digit chunk (4567). This method of remembering phone numbers is far more effective than attempting to remember a string of 10 digits.

(Source : http://en.wikipedia.org/wiki/Short-term_memory)

In an experiment it was observed that out of 10 letters presented a person could recall 7 letters easily. Similarly out of 10 words presented a person could recall 7 words. This is because the words were stored in STM in chunks of letters and not individual letters. Thus regardless of the content, chunking improves the amount of information recalled. Miller offered an explanation to how items are coded in STM using chunking theory.