2.1.2 Short-term memory Flashcards
What is short term memory?
Short-term memory (STM) has the ability to hold a small amount of information for a relatively short period of time.
What is the capacity of STM?
5-9 items.
What is the duration of STM?
18-30 seconds.
What is the encoding of STM?
Acoustic (sound).
What research is there about the capacity of STM?
/Miller (1956). Miller demonstrated this in an experiment where he asked participants to recall information, adding an extra bit as he moved on: A bit like the game ‘I went to the shops’
/Starting participants with two or three words to recall, he gradually built it up until they made an error
/It was found that most participants struggled with between 5-9 words
Evaluation points for STM capacity?
/Jacobs (1887) had completed a similar experiment using digits with 443 female students
/He called this a digit span experiment, using numbers instead of words
/His results were similar to Miller’s, with 7.3 being the average recall
/This supports Miller and suggests his study is valid
/Miller’s study is also reliable as it is easy to copy and it is especially reliable as the results are more often than not the same
/As it is a lab study extraneous variables would have been controlled
/However, it could be argued it lacks ecological validity as the task bears little resemblance to real life
Evidence for duration of STM?
/The main study into duration and STM comes from Peterson and Peterson (1959)
/They gave participants nonsensical three-letter trigrams to learn eg. CGR or BHT
/These were presented visually to the participants, one at a time
/The participants had to recall the trigram in the correct order after a delay of either 3s, 6s, 9s, 12s, 15s or 18s
/During this delay they were asked to complete a distraction task: usually counting backward from 300 in 3s (300, 297,294 etc.)
/This was to prevent them from rehearsing during the delay
/A graph of the correctly recalled trigrams over time was plotted and was shown to be a decay curve
/This demonstrates that over time the memory seems to decay
/The graph was extrapolated to show that after the 30s recall in STM would be zero
/Therefore, Peterson and Peterson stated that the duration of STM was 18-30s
Evaluation points for duration of STM?
/Peterson and Peterson conducted a well-controlled study and many extraneous variables would have been removed or controlled for
/But does it prove decay?
/Could it be that previous trigrams, maybe similar to the one being recalled, interfered with the memory and that is why the participant made the mistake?
/This challenges the validity of the study
Evidence for encoding of STM?
/We know this from a study by Baddeley (1966)
/Baddeley considered encoding in short-term memory and long-term memory but here we will look at STM only
/He gave participants four lists of words to learn:
/Acoustically similar: words that sounded the same such as cat, bat, rat
/Acoustically dissimilar: words that did not sound the same such as laugh, bear, pencil
/Semantically similar: words that mean the same such as large, huge, enormous
/Semantically dissimilar: words that do not mean the same such as police, computer, chair
/The words were all presented visually, on a screen as part of a slideshow
/They had to be recalled in the order presented: Free recall was not allowed
/For the short-term part of the experiment, he asked for a recall immediately
/He found the acoustically similar words had the worst recall
/There was no difference in STM for the semantically similar and dissimilar words
/From this, he concluded that STM relied on acoustic encoding to process information
Evaluation points for encoding of STM?
/Once again, this is a lab experiment so is highly controlled, with extraneous variables taken care of
/However, this also means that it lacks ecological validity as the tasks do not relate to real life
/The words had little to no meaning for participants and so they were harder to recall
/Information we have to recall in reality often has meaning and significance so making recall easier
