Short-term memory is defined as a limited-capacity store that can maintain unrehearsed information for up to about 20 seconds.
	STM also has a limited duration…in other words, information can only be kept there for a brief time before it is lost, unless rehearsal occurs.
	Rehearsal is the process of repetitively verbalizing or thinking about the information–keeping it in use.
	George Miller (1956) wrote a famous paper called “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information," where he illustrated that the average person can hold between 5 and 9 chunks of information in STM.
	A chunk of information is a group of familiar stimuli stored as a single unit. For example, the following numbers 8 -6- 7- 5- 3- 0- 9 can be thought of as 7 individual numbers or they can be chunked together in groups of 2, 3, etc.