Rehearsal is the process where information is kept in short-term memory by mentally repeating it. When the information is repeated each time, that information is reentered into the short-term memory, thus keeping that information for another 10 to 20 seconds (the average storage time for short-term memory).
Short-term memory / primary or active memory - is the capacity for holding, but not manipulating, a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory (when rehearsal or active maintenance is prevented) is believed to be in the order of seconds. The most commonly cited capacity is The Magical Number Seven, Plus or Minus Two (which is frequently referred to as Miller's Law), despite the fact that Miller himself stated that the figure was intended as "little more than a joke" (Miller, 1989, page 401) and that Cowan (2001) provided evidence that a more realistic figure is 4±1 units. In contrast, long-term memory can hold an indefinite amount of information.
Short-term memory should be distinguished from working memory, which refers
to structures and processes used for temporarily storing and manipulating information.
Existence of a Separate Store
The idea of the division of memory into short-term and long-term dates back to the 19th century. A classical model of memory developed in the 1960s assumed that all memories pass from a short-term to a long-term store after a small period of time. This model is referred to as the "modal model" and has been most famously detailed by Shiffrin. The exact mechanisms by which this transfer takes place, whether all or only some memories are retained permanently, and indeed the existence of a genuine distinction between the two stores, remain controversial topics among experts.
The limited duration of short-term memory (~18 seconds without a form of memory rehearsal) quickly suggests that its contents spontaneously decay over time. The decay assumption is part of many theories of short-term memory, the most notable one being Baddeley's model of working memory. The decay assumption is usually paired with the idea of rapid covert rehearsal:
Several researchers, however, dispute that spontaneous decay plays any
significant role in forgetting over the short-term, and the evidence is far from conclusive.
Authors doubting that decay causes forgetting from short-term memory often offer as an alternative some form of interference: When several elements (such as digits, words, or pictures) are held in short-term memory simultaneously, their representations compete with each other for recall, or degrade each other. Thereby, new content gradually pushes out older content, unless the older content is actively protected against interference by rehearsal or by directing attention to it.
Whatever the cause or causes of forgetting over the short-term may be, there is consensus that it severely limits the amount of new information that we can retain over brief periods of time. This limit is referred to as the finite capacity of short-term memory. The capacity of short-term memory is often called memory span, in reference to a common procedure of measuring it. In a memory span test, the experimenter presents lists of items (e.g. digits or words) of increasing length. An individual's span is determined as the longest list length that he or she can recall correctly in the given order on at least half of all trials.
In an early and highly influential article, The Magical Number Seven, Plus or Minus Two, psychologist George Miller suggested that human short-term memory has a forward memory span of approximately seven items plus or minus two and that that was well known at the time it seems to go back to the 19th-century researcher Wundt. More recent research has shown that this "magical number seven" is roughly accurate for college students recalling lists of digits, but memory span varies widely with populations tested and with material used. For example, the ability to recall words in order depends on a number of characteristics of these words: fewer words can be recalled when the words have longer spoken duration; this is known as the word-length effect, or when their speech sounds are similar to each other; this is called the phonological similarity effect. More words can be recalled when the words are highly familiar or occur frequently in the language. Recall performance is also better when all of the words in a list are taken from a single semantic category such as games than when the words are taken from different categories. A more up-to-date estimate of short-term memory capacity is about four pieces or "chunks" of information. However other prominent theories of short-term memory capacity argue against measuring capacity in terms of a fixed number of elements.
Memory loss is a natural process in aging. One study investigated whether or not there were deficits in short-term memory in older adults. This was a previous study which compiled normative French data for three short-term memory tasks (Verbal, visual and spatial). They found impairments present in participants between the ages of 55 and 85 years of age.
Measuring Digit Span and Short Term-Memory
There are many tests to measure digit span and short term visual memory,
some paper- and some computer-based, including the following:
The modification date for all health, and medical content on this page was last updated, and checked on May 8th, 2017 PST U.S.A.