capacity , duration & coding Flashcards
Short-term memory
limited capacity store
Long-term memory
permanent memory store
Capacity
Amount of information that can be held in a memory store
Duration
Length of time information can be held in memory
Coding
Format which information is stored in the various memory stores such as semantic, acoustic and visual.
Capacity of STM: Jacobs (1887)
- used the digit span technique in his lab experiment
- found that the average span for digits was 9.3 & 7.3 for letters
Capacity of STM: Miller (1956)
- reviewed psychological research which concluded that the span of immediate memory is on average 7 items
- did this by observing everyday practices (things that come in 7’s - 7 days of the week)
- developed 7 + or -2
- noticed that people can recall 5 words as well as 5 letters (done by chunking)
Chunking
grouping sets of digits or letters into chunks
Evaluation of capacity STM: validity of the research (weakness)
- Jacobs study is very old and may have lacked control which meant ppts may have not performed as well as they could have ( confounding variable = noise)
Evaluation of capacity STM: validity of the research (strength)
However, it has been replicated and further studies have confirmed the results which support it’s validity
Evaluation of capacity STM: overestimation of the capacity (weakness)
- Miller may have overestimated the capacity of the STM
- Cowan (2011) reviewed research and found the capacity was about 4 chunks
- Suggests that the lower end of Miller’s estimate is more appropriate to use
Capacity of STM
5-9 items
Duration of STM: Peterson & Peterson (1959)
- used 24 students to study duration of STM
- ppts were given a consonant syllable & 3 digit number
- asked to recall the consonant syllable after a retention interval of 3,6,9,12,15,18
- they had to count back from the 3 digit number
- after 3 seconds ppts were 90% correct , after 9 ppts were 20% correct & after 18 seconds 2% correct
- suggests duration is short and less than 18 seconds
Duration of LTM: Bahrick et al (1975)
- tested 400 aged 17-74 on the memory of classmates consisted a recognition test of 50 photos
- in a free recall test ppts were asked to list names they could remember from their graduating class
- ppts tested with 15 years of graduation were 90% accurate in identifying faces & 60% accurate on free recall
- after 48 years it declined to about 70% for photo recognition & 30% on the free recall
Evaluation of duration STM: artificial studies (weakness)
- stimulus material was artificial as the consonant syllable doesn’t reflect real-life memory tasks
- lacks external validity
