Short and Long Term Memory Flashcards
what are the different memory stores? how are they different?
5
short term memory
long term memory
sensory memory/register
each store has different coding, capacity and duration characteristics
they are distinguished by these 3 basic processing operations involved in memory
what is STM?
4
memory for events in the present or immediate past
short duration of 18-30 seconds and will disappear unless rehearsed
limited capacity of 7 +/- 2 items
tends to be coded acoustically
what is LTM?
4
memory for events that have happened in the more distant past
potentially unlimited duration — can last a lifetime
potentially unlimited capacity
tends to be coded semantically
what is capacity?
2
how much data can be held in a memory store
measured in ‘bits’ of information and can be assessed using the digit span
STM: capacity
4
limited capacity
Miller (1956) concluded that the capacity of STM is 7 +/- 2 items — he noted that participants could count 7 dots flashed on a screen but not many more and the same is true for letters and numbers
Jacobs (1887) used the digit span to assess the capacity of STM — participants were presented with a number of digits that had to repeated back in the correct order
he found that the average span for digits was 9.3 items and 7.3 for letters
LTM: capacity
4
potentially unlimited capacity, although information can be lost due to decay or interference
LTM capacity cannot be measured so there are no studies that test it, but there are case studies
Kim Peek — illustrates the capacity of LTM, he is known as the living google as he has exceptional memory despite social difficulties due to his developmental disability
Stephen Wiltshire — known as the living camera because he can look at a landscape and draw an almost perfect replica from memory alone
x3 evaluation points for capacity
lacks ecological validity
challenged by Cowan
individual differences
capacity evaluation
LACKS ECOLOGICAL VALIDITY
4
research into capacity seems to lack ecological validity because the tasks given to the participants lack realism
people rarely have to remember numbers and letters in that manner in day to day life
therefore, findings may not reflect the capacity of STM in ‘real life’ and it may be difficult to generalise these findings to everyday environments
findings may have to be viewed with caution when explaining the capacity of STM
capacity evaluation
CHALLENGED BY COWAN
4
a limitation is that research into capacity is challenged by Cowan (2001)
he reviewed a variety of studies into capacity of STM and concluded that STM is likely to be limited to about 4 chunks rather than 7 items
suggests that STM may not be as extensive as studies like Miller’s suggest and may be even more limited
therefore, research into capacity may be limited in its ability to accurately explain the capacity of STM and the findings should be viewed with caution due to the existence of challenging research
capacity evaluation
INDIVIDUAL DIFFERENCES
4
a criticism of research into the capacity of STM is that is does not consider individual differences
the capacity of STM is not the same for everyone — for example, young adults are more likely to be able to remember more than young children
Jacobs did find that recall increased steadily with age — 8 year olds could remember an average of 6.6 digits whereas the mean for 19 year olds was 8.6 digits
this might be due to a gradual increase in brain capacity or maybe people develop strategies to improve their digit span as they get older such as chunking
what is duration?
1
a measure of how long a memory lasts before it is no longer available
STM: duration
5
short duration
Peterson and Peterson (1959) conducted a trigram retention experiment where 24 students were presented with 3 letters and a 3 digit number
after a retention interval, they had to recall those letters while performing a distractor task such as counting backwards from a large number in 3s
after 3 seconds, 90% recalled the letters correctly but after 18 seconds, only 2% recalled the letters correctly
this suggests that the duration of STM is very limited and usually only lasts 18-20 seconds
LTM: duration
5
potentially unlimited duration
Bahrick (1975) conducted a study where 400 US graduates aged between 17 and 74 were tested on their memory of their classmates
showed participants 50 photos from their high school yearbooks and they had to correctly recall as many names and faces as they could
participants tested within 15 years of graduation were 90% accurate in identifying faces, after 48 years this declined to 70%
suggests duration of LTM is potentially unlimited and can last years
x2 duration evaluation points
lacks ecological validity
results may be due to displacement
duration evaluation
LACKS ECOLOGICAL VALIDITY
4
Peterson and Peterson (1959) may lack ecological validity because the tasks given to the participants lacked realism
trying to memorise consonant syllables does not truly reflect most everyday memory activities because we usually only have to remember meaningful things
therefore, the findings may not be representative of the duration of STM in real life and should be viewed with caution
however, the study may have relevance to everyday life as we often have to remember meaningless, random letters such as postcodes and number plates
