Memory: Capacity, Duration And Coding Flashcards
What’s the capacity of STM?
7 (+/- 2)
Who supported the capacity of STM?
- Millers Magic 7 - most things come in 7s. He also believed we can remember more if we break info into chunks (5-9)
- Jacobs digit span test - mean digit span of 9.3 and letter span was 7.3 for ptps. (443 female students aged 8-19)
What are some of the strengths of research supporting the capacity of STM?
+ Millers theory is supported by jacobs
+ Jacobs research was based on a systematic and replicable procedure
+ Jacobs research has been shown to be reliable and valid as other researchers have replicated his findings
What are some of the weaknesses of the research supporting the capacity of STM?
— Jacobs was in 1800s - not as well controlled so could be affected by confounding variables
— Millers chunking theory has been disproved - people have a shorter span for larger chunks then smaller chunks (Simon 1974) so size of the chunk does matter
— Cowan (2001) reviewed studies into STM and found STM is likely to be limited to about 4 chunks
— Some researchers looked at capacity of STM for visual info and also found 4 items was around the limit (Vogel 2001)
What is the duration of STM?
Very limited - seconds
What did Peterson and Peterson find about duration of STM?
Tested how long ptps can remember 3 letter trigrams for. To prevent rehearsal, ptps counted backwards in 3s from a 3 digit number intill they were told to stop and recall the trigram. Each trial there was a longer duration.
Found items last for approx 18 seconds - as the length of time increases, the ability to recall decreases.
What are some of the problems with Peterson and Petersons duration of STM experiment?
— Lacks ecological validity
— relates to one aspect of memory, but may not apply to all aspects (semantic, episodic, procedural)
— lacks generalisability - 24 psych students - also as they are psych students, they may try and guess the aim of the study and show demand characteristics.
— Single blind techniques can be used to combat this (and Double blind)
What’s some research to support the duration of STM?
Sebrechts et al (1989) - ptps asked to unexpectedly recall 3 words (to avoid rehearsal). If recall was immediate, they did well, but after 4 seconds then recall was almost zero. Supports the idea that STM has a limited duration without rehearsal or processing.
What’s some research against the duration of STM?
STM duration may not be as short - Nairne et al (1999) found that items could be recalled after as long as 96 seconds
However - ptps were asked to recall the same items across trials, whereas in other studies, different items were used for each trial - which would have led to an interference between items, decreasing recall.
Conc - info remains in the STM for quite a while unless other info replaces or overwrites it.
What is coding?
Encoding is the initial learning of info. How the info coming from sensory input is changed into a form so it can be stored in the brain.
What is acoustic encoding?
Coding info by the way it sounds
What is Semantic encoding?
Coding info by meaning
What did Conrad (1964) find about encoding in STM?
If you presented ptps with a list of words that were acoustically similar (e.g. cat, car, cab, etc.) and asked to recall immediately, resulting in them making errors in their recall. Suggests encoding is acoustic in STM.
What did Baddeley (1966) find about encoding in STM and LTM?
Tested effects of acoustic and semantic similarity on recall on 75 ptp. 4 groups given a list of words either acoustically similar or semantically similar or dissimilar. At recall found that ptps had difficulty in remembering acoustically similar words in STM but led to muddled LTM memories. Suggests LTM is stored semantically.
How is STM coded?
Acoustically
