Capacity, Duration, Encoding
Capacity: 7 Chunks +/- 2 Unlimited
Duration: 20 seconds Unlimited
Encoding: Acoustic & visual Semantic
Duration of STM
Peterson and Peterson (1959)
24 students were asked to complete nonsence trigrams e.g WRT 303 (the idea was to remember this after prevention of rehearsal was completed) The prevention was counting back in 3's from the number you started with. Each test lasted either 3,6,9,12,18,20 seconds
Results: 90% had accurate recall at 3 seconds - this is because the duration of prevention of rehursal was minimal compared to the 2% that remember at either 18 or 20 seconds
Validity? - Lacks ecological validity as it can't be assossiated with a task that we may do in our lives. It is also a lab experiment and therefore people may suffer from demand characteristics.
Capacity of STM
George Miller (1956) - magic number 7 + OR - 2 - How many chunks of information you could remember
Cowan (2001) - suggested that it was atchually 4 chunks of information - suggesting that it wasn't as extensive as first thought
Vogel et al (2001) - thought that visual encoding in STM was limited to 4 chunks - showing that encoding was also though visual not just verbal in STM
Josef Jacobs (1887) - used the digit span technique:
Remembering a list of numbers by looking at the first, covering it up, recalling it and then adding the second number to the list, repeating till you can't remember all of the digits in the list.
Results: Recall for digits = 9.3, whereas recall for letters = 7.3 - more likely to remember digits because there is less of them - leaving less room for variation
JJ also investigated whether capacity increased with age and found the digit span for 8 year olds is 6.6 whereas as for 19 year old it is 8.6 - suggesting his hypothesis is true. This could be due to increase in brain capacity and known use of memory stratagies
Semantic - though meaning
Acoustic - thorugh sounds
Baddely (1966) - looked at acoustic and semantic encoding in short and long term memory. Asked participants to recall words that were either acoustically or semantically similar or dissimilar.
Results: Easier to remember semantically similar in ST and acoustically similar in LT
Multi- Store Model
Sensory Memory: this is taken in through an environmental stimulus (what you see around you), you don't often notice you are looking at, and unless important it is not transfered into STM memory
The duration of sensory memory is extrememly limited (0.5 seconds).
Sperling (1960) - asked participants to look at either a grid of letters and numbers or a row for 50 milliseconds (a blink of an eye) and asked to recall what they could remember
Results: For the entire grid they were able to recall 5 items with 42% accuracy and at three items they were 75% accurate
This showed that sensory memory has a duration of approximitly 0.5 seconds and that the capacity of it is approximitly 5 items
Serial Position Effect
Glanzer and Cuntiz (1966)
Gave participants 20 words to remember (each shown individually)
Results: Able to remember the first few words (primacy effect) because they had been stored into LTM and the last few words (recency effect) because these are still in your short term capacity
Validity? - Labotory experiment and therefore lacks realism and would also cause demand characteristics of the participants
Weakness of Multi-Store Model
- It is very vague and doesn't go into detail about any of the stores
- Shows STM and LTM as unitary stores whereas later research has proved this not to be the case - EVIDENCE FOR THIS... KF suffered brain damage, could use visual representations and image images still but he was unable to verbally communicate
Spires et al (2001) - 147 patients with amnesia, their procedure and representation were ok but everything else wasn't. This shows that LTM is not a unitary store
Validity - all evidence here has ecological validity and it was an observational study - this could mean the experimenter sees what they want to see, however here it is clear that they are or aren't able to do something and therefore this is unlikely to happen.
Strengths of Multi-Store Model
Simple structure - easy for anyone to follow and understand and gave psychologists a basic idea of how the memory works
Clearly identifies that there are different stores of memory and how we use them, which has been backed up by research
Studies in support:
- Murdock (1962) Serial Position Effect
Working Memory Model
Limitations and Strengths of WMM
- Not much is known about the Central Executive
- Evidence suggests the central executive is not unitary
- The link between working memory and LTM is not fully explained
- The working memory model explains not only the storage, but also the processing of information.
- Specificity. Because the model proposes specific and separate functions and subsystems, new predictions and hypotheses can be drawn up for testing.
- It is consistent with PET scans of brain-damaged patients.