Read to someone a series of words that have no connection with one another and then ask him/her to repeat them. Start with 1 word, then 2 different words, then 3 different words, and so on. When you get up to about 7 words, chances are the person will start making mistakes. That’s because our short-term memory can hold only a limited number of separate items. The average is about 7 items, plus/minus 2, depending on the individual.
The childhood events, the place where we left our keys, the lessons from the class- memory does a lot of things for us and helps to make us who we are. Short-term is the capacity of holding a small amount of information in mind in an active, readily available state for a short period of time.
Experts believe that you can hold approximately seven items in short-term memory for about 20 to 30 seconds. Short term memory has three key aspects:
1. Limited capacity (only about 7 items can be stored at a time)
2. Limited duration (storage is very fragile and information can be lost with distraction or passage of time)
3. Encoding (primarily acoustic, even translating visual information into sounds).
Psychologist George Miller in his 1956 paper suggested that the capacity of an adult’s short-term memory for storing a list of items was somewhere between 5 and 9. He gave the Magic number 7 (plus or minus two). Miller thought that short term memory could hold 7 (plus or minus 2 items) because it only had a certain number of “slots” in which items could be stored.
However, the amount of information that can be held in each of these slots was not defined by Miller. This capacity can be stretched somewhat by using memory strategies such as chunking, which involves grouping related information into smaller "chunks."
Jacobs in his 1887 study used the digit span test with every letter in the alphabet and numbers apart from “w” and “7” because they had two syllables. He observed that recalling numbers was easier as compared with letters for people. The average span for letters was 7.3 and for numbers was 9.3.
According to the study by Atkinson and Shiffrin in 1971, the duration of short term memory was recorded to be between 15 to 30 seconds. Items can be kept in short term memory by repeating them verbally (acoustic encoding), a process known as rehearsal.
Using a technique called the Brown-Peterson technique which prevents the possibility of retrieval by having participants count backwards in 3s, Peterson and Peterson (1959) showed that the longer the delay, the less information is recalled. The rapid loss of information from memory when rehearsal is prevented is taken as an indication of short term memory having a limited duration.
Baddeley and Hitch (1974) have developed an alternative model of short-term memory which they call working memory.
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