short and long term memory stores

capacity

how much data can be held in a memory store

what capacity does STM have?

short-term memory (STM) has a limited capacity store

what capacity does LTM have?

long-term memory (LTM) has a potentially infinite capacity

how do we assess the capacity of STM?

using digit span tests. Miller (1956) reviewed several studies and concluded that STM capacity was 7 +/- 2 items.

what is an example of Miller’s digit span theory?

for example, when dots were flashed on a screen, participants were reasonably accurate with their recall when there were seven dots but very inaccurate with 15 dots.

what is Miller’s chunking theory?

Miller also found people can recall five words as well as they can recall five letters - they do this by chunking - grouping sets of digits or letters into meaningful units.

duration?

the measure of how long a memory lasts before it is lost.

what is the duration of STM?

STM has a duration of less than 18 seconds unless items are rehearsed

what is the duration of LTM?

LTM potentially lasts forever.

what was Peterson and Petersons study into duration?

they found that ppts were 90% correct in their recall of consonant syllables after 3 seconds, but only 2% correct after 18 seconds

what was Bahrick et al’s photo-recognition theory?

ppts could remember the names of former classmates with 90% accuracy within 15 years of graduation - this declined to 70% after 48 years

what was Bahrick’s free recall theory?

ppts free recall was 60% accurate after 15 years, dropping to 30% after 48 years

coding?

refers to the way in which information is changed so that it can be stored in memory

how is STM coded?

STM is largely encoded acoustically

how is LTM coded?

LTM is largely encoded semantically - this produces more durable memory traces in LTM

what was the procedure of Baddeley’s coding theory?

had four groups learn different word lists:

A) acoustically similar

B) acoustically dissimilar

C) semantically similar

D) semantically dissimilar

what was Baddeley’s results?

when STM was tested, group A (acoustically similar words) had the worst recall.

when LTM was tested 20 minutes later, group C (semantically similar words) had the worst recall

capacity - ao3 - Baddeley is unreplicatable?

Cowan reviewed studies on the capacity of STM and concluded that STM is probably to four rather than seven ‘chunks’

* suggests that STM is not as extensive as the 7+/- 2 claimed by Miller

duration - ao3 - results may be due to displacement?

It could be argued that Peterson and Peterson’s research did not measure what it set out to measure.

* counting back numbers may have ‘displaced’ the syllables to be remembered
* Reitman used auditory tones rather than numbers and found duration of STM was much longer.
* suggests that Peterson and Peterson’s research was due to displacement rather than decay

coding - ao3 - STM may not be exclusively acoustic?

some studies have shown that visual codes are also used in STM

* Brandimote et al found that ppts used visual coding in STM when they were given pictures to remember and prevented from verbally rehearsing
* suggesting that there may be multiple types of coding in STM

coding - ao3 - LTM may not be exclusively semantic?

in general LTM appears to be semantic, but not always

* Frost found that LT recall was related to visual swell as semantic categories
* Nelson and Rothbart found evidence for acoustic coding in LTM
* suggests that LTM can be encoded differently depending on what the information is