coding capacity and duration of STM and LTM Flashcards
(23 cards)
what is coding
the way information is represented in the memory store e.g. sound, meaning, image
what is capacity
the amount of info that can be held in the memory at any time
what is duration
the length of time that memory can be held
what is the sensory register
a set of limited capacity, specific stores. if info isnt rehearsed it will decay. sensory register stores for a fraction of a second
what is short term memory
limited capacity memory store. information is mainly coded accoustically. capacity is 7+/- items. The duration is 18 seconds.
what is the long term memory
permanent memory store. in LTM info is mainly coded semantically meaning it has unlimited capacity and memories can be stored for lifetimes.
what is memory
the process of storing and retrieving information about the past
who tested how STM and LTM were coded and how
baddeley tested coding. he did this by using accoustically similar but semantically different words such as cat, cab, can. and words that are semantically similar but accoustically different such as big, large, huge. pps had difficulty remembering semantically similar words in LTM and accoustically similar words in STM.
limitations of baddeleys research
- used artifical stimuli
- frost (1972) showed long term recall was related to visual as well as semantic categories
- nelson and rothart (1972) found evidence of acoustic coding in LTM
- low validty as LTM was tested fro 20 mins so is it really LTM?
strengths of baddeleys research
identified a clear difference between the two memories
why is the validity of baddeleys study questioned
LTM was tested over 20 minutes so is it really long term memory
what was jacobs (1887) technique for measuring STM
the researcher gave 4 digits and the pp had to recall these in the correct order. if the pp got them correct the number of digits would increase until they no longer got them correct. this determines the individuals digit span
what was the mean digit span for jacobs pps
7.3
what was millers observation (1956)- magic number 7
things happen in 7’s e.g. days of the week. most people have a capacity of 7 +/- 2
how do you extend STM capacity
chunking info together
what did Cowan (2001) say about millers estimate
reviewed other peoples research and concluded the capacity of STM was only 4 chunks. this suggests that the lower ends of millers estimate (5 items) is more appropriate than seven items
1 limitation of millers study
over estimated the capcity of STM
1 limitation of cowen
uses artificial stimuli so low ecological validity
outline peterson and peterson (1959) procedure to test duration of STM
-tested 24 students in 8 trials
-each trial a pp was given a consonant syllable and a three digit number.
-they were asked to recall the consonant syllable after a retention period of 3, 6, 9, 12, 15 and 18 seconds. during retention pp has to count backwards from the 3 digit number to prevent motor rehearsal
what were the results of peterson and peterson (1959) procedure
The % recall was:
- 80% after three seconds
- 50% after six seconds
- 3% after eighteen seconds
STM duration is 18 seconds long unless verbal rehearsal is involved
3 limitations of peterson and peterson (1959)
- tasks were artificial and not a good way of testing how we remember things in everyday life so low validity
- the loss of info could be due to STM limited capacity not duration as counting task may have displaced trigram therefore affecting validity
- it is possible that trigrams presented earlier caused confusion (pro-active interference) for the pps and so later trigrams were incorrectly recalled
outline the procedure of duration LTM bahrick (1975)
- 392 graduates of an american high school were asked to put names to faces of their high school yearbook
- memory tests uincluding recognising pictures, matching names and recalling names with no picture
what were the findings of duration LTM bahrick (1975)
- participants up to 34 years old recalled very well
- performance was better on recognition than recall tasks
- after 47 years, pps dipped in remembering
