duration of memory Flashcards
what is the duration of memory in the STM and LTM?
STM:
limited duration - around 18 seconds.
LTM:
potentially unlimited.
define duration.
the length of time information can be held in a memory store.
who conducted research into the duration of the STM?
Peterson and Peterson (1959).
outline the research of Peterson and Peterson (1959).
tested 24 students in eight trials each.
on each trial the experimenter said out loud a trigram (e.g. YCG) for the student to remember.
to prevent rehearsal that would increase the duration of STM memory for the trigram, they were also given a 3-digit number (e.g. 565), and had to count backwards in threes until they were told to stop.
on each trial the students were told to stop after varying durations - 3,6,9,12,15 or 18 seconds.
after 3 seconds, average recall was around 80%, after 28 seconds it reduced to around 3%. their findings suggested that STM duration is around 18 seconds, unless there is verbal rehearsal (repeating the info over and over).
discuss ecological validity as a limitation of Peterson and Peterson (1959).
lacks ecological validity.
the stimulus material of a trigram used in the lab experiment was artificial. although the study is not completely irrelevant because we do sometimes try to remember meaningless material (e.g. phone numbers), recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful.
this means the study lacks ecological validity and cannot be applied to most everyday situations.
additionally, the study only related to one aspect of memory and may not apply to all aspects, such as semantic, episodic and procedural - thus reducing the value of the research support for duration of memory.
discuss population validity as a limitation of the research by Peterson and Peterson (1959).
they used students, which are not representative of the entire population due to their age and education.
this means that the findings of the study cannot be generalised to the wider population, reducing its population validity - thus limiting the support it can give duration of STM.
discuss research support as a strength of the research by Peterson and Peterson (1959).
a strength is research support.
research has found that when ptps were asked to unexpectedly recall 3 words.
recall was very good when recall was immediate, but after 4 seconds recall was almost 0%.
this supports the idea that STM has a limited duration without rehearsal.
however -
more recent research shows that P&P may have underestimated the duration of the STM.
research has found that items can be recalled after as long as 96 seconds.
While this does limit the validity of P&Ps findings, in this study, ptps were asked to recall the same items across trials, whereas in the earlier study different items were used for each trial - which would have lead to interference between items, decreasing recall - which could explain the difference in duration findings. this interference is more representative of real life memory application, which gives value to P&Ps theory of duration in the STM.
describe duration of memory in the LTM.
theoretically potentially unlimited.
there are individual differences, and those who practise and use strategies can increase their memory capacity and duration, but so far there has been no found clear limit to the duration or capacity of the LTM.
who conducted research into the duration of the LTM?
Bahrick et al (1975).
outline the research by Bahrick et al (1975) into duration of the LTM.
studied 392 American ptps aged between 17-74.
Obtained the ptps high school year books.
recall was tested in various ways, including:
- photo recognition test consisting of 50 photos, some from their yearbook.
- free recall test, names of people in their graduating class.
15 years - 90% accurate in photo recognition.
48 years - declined to 70% for photo recognition.
free recall was less accurate.
15 years - 60%.
48 years - 30%.
shows that LTM may last up to a lifetime for some material.
photo was better than free recall, so also suggests that in real life we require something to jog our memory - that it is there, but cannot always access it.
evaluate the research by Bahrick et al (1975).
high external validity.
this was not a lab experiment, and the researcher investigated meaningful memories (e.g. names, faces) - the data is more true to real life. when studies on LTM were conducted on meaningless photos to be remembered, recall rates were lower.
this suggests that Bahrick et al’s findings reflect a more real life estimate of the LTM, giving value to the research and thus its theories about the duration of the LTM.
