Memory- Coding, Capacity And Duration Of Memory Flashcards
Coding
The format in which information is stored in the various memory stores
Capacity
The amount of information that can be held in a memory store
Duration
The length of time information can be held in memory
Short-term memory (STM)
The limited capacity memory store.
Coding is mainly acoustic (sounds)
Capacity is between 5 and 9 items on average
Duration is between 18 and 30 seconds
Long-term memory (LTM)
The permanent memory store.
Coding is mainly semantic (meaning)
Capacity is unlimited
Duration is a lifetime
Research on coding
The process of converting information from one form to another is called coding.
Baddeley (1966) gave different lists of words to four groups of ps to remember:
Group 1- acoustically similar words (cat, cab, can)
Group 2- acoustically dissimilar words
Group 3- semantically similar words (great, large, big)
Group 4- semantically dissimilar words
Ps were shown the original words and asked to recall them in the correct order.
When they had to do the recall task immediately after hearing it (STM recall), they tended to do worse on the acoustically similar words. Meaning that STM is coded acoustically as similar sounding information conflicted with each other.
When they had to do the recall task after a time interval of 20 mins (LTM recall), they tended to do worse on the semantically similar words. Meaning that LTM is coded semantically as information with similar meanings conflicted with each other.
Research into capacity
Jacobs (1887)
Developed the DIGIT SPAN technique, where a ps has to immediately recall a sequence of letters or numbers which increased by one letter or number with each trial that they got correct until they got it wrong.
The mean span for letters that could be correctly recalled was 7.3, and for numbers it was 9.3
Miller (1956)
Concluded that the capacity of STM is 7 plus or minus 2 ‘bits of information’
Noted that things usually come in sevens ( 7 days of the week, 7 deadly sins)
He noted that in order to increase the capacity people ‘chunk’ information together (grouping digits or letters into units or chunks)
Ppl recall 5 words and 5 letters (chunking)
Capacity of LTM is unlimited
reserach into duration
STM duration was investigated by Peterson and Peterson (1959). Ps were given a nonsense ‘trigram’ of three syllables, together with a three-digit number (for example, ‘TJF 374’). To prevent rehearsal, they had to count backwards in threes from the number until told to stop after either 3,6,9,12,15 or 18 seconds. After the interval, they had to recall the trigram . Recall was generally accurate after 3 seconds (over 80%), but by 18 seconds it declined to around 10%. It was concluded that the duration of STM is around 18-30 seconds, if rehearsal is prevented.
LTM duration was investigated by Bahrick et al (1975). ps were aged between 17 and 74, and were required to idenitfy schoolmates from their high school yearbook, name them in a free recall test, or match photos to names. ps who had left school within 15 years were very accurate with photo recognition (90%), but even those who had left decades earlier were still 70% accurate. Older ps were less good at free recall, but nearly as good as younger ps in the matching task. The conclusion was that the duration of LTM is potentially lifelong.
evaluation (AO3)
many studies such as these use artificial and meaningless stimuli (Baddeley’s word list). This is a weakness because they do not refelct how memory works in everyday life, so they lack external validity.
Jacob’s study was conducted a long time ago, so may not have been done to the same scientifically rigourous standard as research today, therefore the validity of the findings is in question
Bahrick’s study used more meaningful material, so is higher in external validity, however it is very hard to control variables in a study such as this, as it is unknown how many ps may have looked at their yearbook in the intervening years, for example. (studies on LTM using meaningless material, resulted in lower recall rates Shepard 1967)
